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AC Not Working | Central Air Conditioning Repair & Troubleshooting

clean air conditioner©Don Vandervort, HomeTips

Clean the central air conditioning compressor, located outdoors, before every cooling season.

Is your AC not working? If your central air conditioner is not cooling right, save money, time, and get comfortable again with these expert DIY air conditioning troubleshooting and repair techniques.

Need help NOW? Get a HomeAdvisor Air Conditioning Pro Fast!

In brief:

If your AC is not working at all:

1. Be sure it is receiving power at the electrical panel.
2. Reset the equipment’s switches and/or overloads. 
3. Check the thermostat settings.
4. Check the condensate overflow switch (see below).

If your AC is not cooling but runs:

1. Turn off the power.
2. Clean or change the filter.
3. Look to see if ice has formed on the coils and, if it has, turn on the power and the fan to melt it.
4. Clean the condensate drain (see below).
5. Finally, check and clean the outdoor compressor.

HA2016 Air-Conditioners---Central

Now, In-Depth Answers to Your AC Problems:

Several different kinds of problems can occur with a central air-conditioning system. We discuss some of the most common ones below:

• AC not working at all
• AC not cooling well but runs
• Room temperature too hot or too cold
• Water leaks from air conditioner
• Air conditioner makes strange noises
• Air conditioner won’t turn off

Although a qualified air-conditioning repair person should handle certain types of central air conditioner repairs, you’ll find methods for handling simple repairs and maintenance yourself in this article.

In addition to the information below, see these two articles for the general care and maintenance of your air conditioner: Preparing Your Air Conditioner for Summer and How to Replace Furnace & AC Filters. Most noteworthy, you should replace the filters at least twice a year, before the heating and cooling seasons.

Central AC Not Working At All

Be sure the thermostat is set to "Cool" if your AC won't go on.© Mariusz Blach |

First make sure the thermostat is set to “Cool” if your AC won’t go on. Shop for programmable thermostats now.

If your central air conditioner won’t go on automatically when the thermostat signals the need for cooling:

1Check the main electrical panel and any secondary circuit panels for a tripped breaker or blown fuse. If you find the problem there, reset the breaker by turning it off and then on or replace the fuse. A central air conditioner typically connects to a dedicated 240-volt circuit.

If the breaker continues to trip, suspect a short in the system—in the compressor, capacitor, or the fan motor. Hire an electrician to track down and solve this problem.

2Make sure the thermostat is set to COOL and its temperature setting is at least 3 degrees below the ambient room temperature.

3Make sure the power is on. Check the switch in the furnace or air handler, and the outdoor condenser. Also make sure no one has shut off the compressor’s 240-volt disconnect, typically in a metal box mounted near the compressor.


With this type of electronic thermostat, you pull off the body to access the baseplate and wires.

4Remove the thermostat’s cover after turning off the power to the air conditioner. Remove the thermostat’s body from the base (usually by pulling straight out) and replace the batteries (if it has batteries). Make sure all wires securely attach to their terminals and that the cover won’t pinch them. Replace the cover and wait 3 or 4 minutes, and then try the system again.

5If that doesn’t do the job, open the thermostat and unscrew the wire from the Y terminal. Turn the power back on. Holding the wire by its insulation only, touch the bare end to the R terminal and hold it there for about two minutes. If the compressor kicks on, the thermostat is faulty; replace it as discussed in the article How to Install an Electronic Thermostat. If the compressor doesn’t go on when you hold the Y wire to the R terminal, turn the power back off and either call an air-conditioning technician or check the capacitor.

6Finally, check the compressor’s capacitor and wires. The capacitor in the compressor starts both the condenser and the fan. If the capacitor has failed, the A/C unit will not run. It’s very easy to test whether it works and it is cheap and easy to fix if it doesn’t.

How to Test the AC Compressor’s Capacitor

Before opening the electrical cover on the A/C unit, be sure to shut off all power to the unit and verify that it is off. Next, remove the cover and, using a digital multi meter set to “Capacitance,” put one lead on the “Common” terminal and the other lead on one of the other two terminals. The meter should show a number—not “OL” which indicates a short. A/C capacitors can be like two capacitors in one, with both sharing the common leg.

Here is a video that shows more precisely how to do this. Tip: Take a quick digital photo of the wires before disconnecting them so you know where to replace them.

How to Test an Air Conditioning Condensing Unit Capacitor and Wires from oliverfails on Vimeo.

Still not working? Please read “Air Conditioner Not Blowing Air,” below.

HA2016 Air-Conditioners---Central

AC Not Cooling Well

If you can hear your central air conditioner running, but it doesn’t cool well, make sure nothing is blocking or limiting air flow anywhere in the system—the air filters, registers, and the compressor. For more about filters, see How to Replace Furnace & AC Filters.

A kinked refrigerant line, or a blower fan that isn’t running right can cause this, too. Next, check the air handler:

How to Check the Indoor Air Handler

1Turn off the power to the air conditioning air handler or furnace. If the air handler is a gas furnace, turn off the gas at the gas valve that serves the furnace.

2Remove the door on the front of the air-handler cabinet so you can access the filter. Pull out the filter and clean or replace it as necessary.

3Look for ice. If you see ice in the area around the coils, close the unit back up, turn the power back on, and turn on the fan. The ice should melt within an hour or two.

Ice In the AC Air Handler

Only two things cause an AC air handler to freeze up: 1) reduced air flow because of dirty filters, coils, or poorly working fans, and 2) low refrigerant level, which a pro must check and, if necessary, recharge. More often than not, the problem comes from reduced air flow.

Clear the Condensate Drain

Air conditioners can create a lot of water because they remove moisture from the air. To get rid of this, they have a [usually plastic] drain pipe that comes out of the side of the air handler. Over time, algae can block this pipe and, when it does, the AC won’t work. In fact, some condensate drains have a float switch that won’t let the AC run if water backs-up. Water can also puddle around the unit or flood the area. To deal with condensate problems, please see Air Conditioner Leaks Water, below.

How to Check the Outdoor Compressor

1Turn off the power. Before cleaning the compressor, shut off all power to the unit and verify that it is off.

2Clean the outdoor compressor. For complete instructions, please see Air Conditioner Doesn’t Cool Well. This video does a good job of showing you how to clean the coils:

3Make sure the compressor is working. When you set the thermostat to a temperature below the room temperature, you should hear the outdoor compressor run and see the fan turning inside the top. If the fan isn’t turning, look for an overload button or switch to reset (not all types have this). Stick a screwdriver or stick down through the top grille and try to spin the fan blades clockwise. They should spin freely. If doing this gives the fan enough of a boost to get it going, the unit has a faulty capacitor that must be replaced. See Step 6 under Central AC Not Working At All, above.

4 Finally, have the coolant checked. If none of these steps workedthe coolant may need recharging by an air conditioning professional. Call a qualified local AC professional—this is not something you can do yourself.

If your room has dramatic swings in temperature before the system kicks on, see Room Temperature Too Hot, Then Too Cold.

Air Conditioner Not Blowing Air

If your AC doesn’t go on at all when you set the thermostat for a cooler-than-room temperature, please read Central AC Not Working At All, above. Then, if you have fairly good DIY skills and a multimeter, go through the diagnostic steps in this video to determine whether the problem may be a condensate pump switch.

If Your Air Handler Doesn’t Blow Air Properly

If the air handler doesn’t blow air properly, the indoor evaporator coil may be dirty or frozen up. Reduced air flow, whether caused by dirty filters, a dirty coil, dirty squirrel cage blower, or a broken fan motor can cause the coil to freeze up, blocking air flow.

If your air handler’s motor runs but the blower doesn’t move air, the belt that connects the two probably has broken. Replacing it is an easy fix if you have a few tools and do-it-yourself skills.

Replacing an AC Blower Belt

Here’s how you can replace the air conditioner’s blower belt:

1Turn off all power to the unit and, if the air handler is a gas furnace, turn off the gas at the gas valve that serves the furnace.

2Remove the door on the front of the air-handler cabinet to give you access to the blower (it might be on a slide-out drawer.) Check the number stamped on the belt and get an exact replacement from a home center or heating supply outlet.

ac not working motor pulley©HomeTips

First, fit the belt onto the motor pulley.

3You can usually slip the belt on the motor’s (smaller) pulley first and then start it on the blower pulley, as shown at right. Rotate the blower pulley by hand, holding the belt in place but keeping your fingers from getting caught between the belt and the pulley. The belt should slip right into place. If it seems to be too tight or difficult to set in place, it may be necessary to adjust the motor mount to provide more slack. Then you can re-tighten the tension once the belt is in place. Check the manufacturer’s specifications for proper tension—in most cases, the belt should deflect about an inch when you press down on it.

4Lubricate the blower. Finally, some blower motors need oiling. Note: Those with sealed bearings don’t. If recommended by your maintenance manual, oil the bearings according to the manufacturer’s directions.

AC Blower Hums But Doesn’t Run

If the air handler’s blower motor hums but doesn’t run, you’ll probably need to replace the blower motor. This video shows how to replace the motor.

AC Air Handler Doesn’t Run

If the air handler doesn’t run at all, it may not be receiving power. Check its circuit breaker, and any switch that controls it at the air handler or furnace cabinet. Then check the door switch—a small switch inside the metal door that prevents the appliance from running when the cabinet is open. Also check the thermostat. For more, see Central AC Not Working At All, above.

Water Leaking from AC

Air conditioners and high-efficiency combustion furnaces create significant condensation—we’re talking about a lot of water, especially in humid climates—several gallons per day. Consequently, this water must exit the air handler—typically through plastic pipe or a drain tube. That drain tube goes directly outside, often terminating near the compressor, or to a floor drain or to a small electric “condensate pump” located by the air handler. Where a condensate pump is used, it connects to a 1/2-inch vinyl or rubber tube that exits outdoors or to a drain.

Water at the Base of the Air Handler

Water dripping or pooling at the base of the air handler indicates: 1) a leak from one of the plastic pipes or tubes that carry it, 2) something may be blocking the water’s flow, or 3) the condensate pump may not be working. If the pump stops working, it will overflow.

air conditioner float switchRectorseal

Float switch is designed to shut off the A/C unit if the drain becomes clogged.

On some air handlers, the condensation drainpipe has a small safety float switch (see photo) connected to it. If the drainpipe backs up with water, the float switch will shut off the air conditioner. This is a sure sign that it’s time to clear the condensation drainpipe.

1 If your system includes an electric condensate pump, make sure it is connected to a working electrical outlet. Then look to see if the tubing that carries away the water has come loose from the pump. If it has, reconnect it.

More likely is the possibility that the tube or the pump is clogged with algae. If this is the case, use a wet-dry vacuum  to suck all of the water out of the tube. In some cases, it might be easier to replace it with new 1/2-inch tubing purchased online, at an HVAC supply shop, or at a well-stocked home improvement center.

ac not working condensate pump©Don Vandervort, HomeTips

The condensate pump, next to the air handler or furnace, is easy to replace. A new one costs about $50.

2 Test the pump by pouring water into its collector. The pump, which is turned on by an inner ball float that rises with the water level, should start. A stuck or broken ball float won’t rise. If it’s stuck, disconnect the pump from the power and from the inbound tubes, disassemble the top, and clean it out thoroughly. With an old or broken float, you’re probably better off replacing the condensate pump so you don’t have to do this again in the near future.

To kill algae, pour a dilute solution of bleach (1 part bleach to 16 parts water) into the pump’s trough and pump it out through the tube. Don’t do this on you lawn—it will kill the grass.

3 If the pump runs but doesn’t empty the trough, the ball-like check valve just before the discharge tube is probably stuck. Unscrew the check valve, loosen the ball inside, and look for an obstruction and a build-up of algae. If it appears that a condensation drain tube is clogged with algae, remove it if possible (you may have to cut it and replace it later with a coupling). Blow it out or run a wire through it to clear it—or, better still, replace it with new tubing.

4 Ice may be blocking the tube. If this is the case, clean or change your AC filters. If the filters appear to be fine, the air conditioner’s refrigerant supply is probably low. Call an air-conditioning technician to have the unit recharged.

For more about filters, see How to Replace Furnace & AC Filters.

HA2016 Air-Conditioners---Central

Air Conditioner Makes Noise

Noises sometime occur in the indoor air handler, the outdoor compressor, or the ductwork.

Air Handler Makes Noise

Problem noises in an air handler are squealing, grinding, and buzzing.

AC air handler squealing or grinding noises. Though most air handlers have direct-drive motors, some older units may be belt-driven. Squealing sounds from a belt-drive air handler generally occur when the belt that connects the motor to the blower slips. In most cases, the belt is improperly aligned or worn and needs replacement. Follow the instructions above under Air Conditioner Doesn’t Blow Air and refer to your owner’s manual.

If a direct-drive blower is squealing or making a grinding noise, shut off the unit and—unless you’re an accomplished do-it-yourselfer—call an HVAC professional—the motor’s bearings are probably shot. If you can handle this type of work, you can order and replace the motor.

AC air handler buzzing sounds. Do you hear a buzzing sound when you turn on the thermostat? The only thing that comes on in the house when you turn on the thermostat is the fan relay and fan in the air handler or furnace. Try switching the thermostat HEAT/COOL switch to OFF. Then switch the fan switch from AUTO to ON. The fan (only) should come on. If the air handler makes a buzzing sound, it probably has a bad fan relay or, more likely, blower fan.

Outdoor AC Compressor Makes Noise

Outdoor compressors sometimes make buzzing, humming, or grinding noises.

AC compressor buzzes. If the outdoor AC unit makes a buzzing sound, as though it wants to turn on but can’t, the run capacitor may be defective. If that capacitor goes bad, the motor will overheat when it tries to turn on but can’t get started. When the motor overheats, a thermal overload switch will shut it off.

When it buzzes, quickly poke through the grille with a long screwdriver or stick to try to spin the fan clockwise (be careful!). If it starts spinning, it will run for one cycle but then stop working again. This indicates that the capacitor is bad and needs to be replaced. (See Central AC Not Working At All, above.)

AC compressor hums. If the outdoor compressor hums when you switch the thermostat to COOL, the problem could be the low voltage transformer on that unit—something that would need to be checked by a pro.

AC compressor grinding noise. Over time, the bearings in the motor can wear out. The result is a grinding sound and, in many cases, the motor will overheat and shut off. When this happens, it’s time to replace the motor.

Noisy Ductwork

Many heating/cooling ducts are metal so they conduct noise quite readily from the air-handling unit to your rooms. To break the conduction of sound, you can have a heating contractor insert flexible insulation ductwork between the heating/cooling system and the metal ductwork.

HVAC professional checks the refrigerant levels in an air conditioning system.© Ernest R. Prim /

Hire a pro for complex repairs. Here, an HVAC professional checks the refrigerant levels in an air conditioning system. Get an HVAC pro now.

Ductwork pinging or popping. If you hear a pinging or popping sound coming from metal ductwork, this may be caused by thermal expansion or by air blowing past a loose flap of metal. Track along the duct runs, listening for the sound. If you find it, make a small dent in the sheet metal to provide a more rigid surface that’s less likely to move as it heats and cools.

Furnace or air handler rattling ductwork. If the furnace makes rattling noises when it runs, be sure the cover panels are screwed on tight. If they aren’t, tighten them.

Air Conditioner Won’t Turn Off

If your AC doesn’t turn off when room temperature reaches the temperature set on the thermostat, the problem is generally occurring either at the thermostat or in the electrical system that runs the outside condensing unit. You can use the AC’s circuit breaker to shut off the unit, but that should not be a permanent solution—circuit breakers are not designed to be used like light switches.

If the thermostat is blank—not displaying any values—or if the AC shuts off when you switch the thermostat to HEAT, the thermostat is probably broken and needs to be replaced. Please see Home Thermostats Buying Guide.

If the thermostat works fine with the furnace, the issue probably isn’t the thermostat unless one of the wires has disconnected or arced. When the AC is running, try removing the yellow low-voltage wire from the thermostat. Then:

If the unit turns off, either the thermostat is broken or it is wired improperly. Make sure it is wired correctly—with no cross-connected wires. If the wiring appears to be okay, buy a new thermostat and install it according to the instructions.

If the AC doesn’t turn off, the contacts on the outdoor run relay may have welded together—something that can happen over time because of frequent electrical arcing at the relay. Before checking the run relay, turn off the power to the furnace and the condensing unit. Next, disassemble the relay and pry apart the contacts. This should do the trick until you buy a replacement—which you should do soon.

 More Answers Below!

Hey, if we didn’t answer you question yet, check the conversation board at the bottom of this page…lots of new answers and help there!

Getting the Work Done

get an a/c service pro
By keeping your AC unit working well, you can save energy and, as a result, money. If a central air conditioner is in ill repair, it probably won’t work when you need it most.

If you would rather hire an air-conditioning pro to inspect and maintain your AC equipment, HomeAdvisor’s FREE service will help you find a qualified local AC professional.

Call for free estimates from local pros now:

Join the Conversation

  • Carla Salyers

    help! Need assistance troubleshooting my Central AC unit. Recently my AC has stopped turning itself off when it reaches the desired temperature that is set at. I hear a click where its trying to switch off but instead it keeps going. sometimes it continues to cool and others it continues blowing but not cold air. Trying to see if this is a thermostat issue or unit issue. thank you.

    • cashmemorz

      Having the same problem. Thermostat set to off but a/c still going. Flipped circuit breaker for a/c to off. Set thermostat to heat. Furnace works fine. Will check for model of a/c. Will inquire on line about thermostat and a/c model. Might have to replace thermostat. See if this helps you.

    • Pat McBride

      The contacts in the outside relay will weld together sometimes. I have found this many times. Turn the power off to your furnace as well as the outside condensing unit. Dissemble the relay and pry the contacts open, You should follow up with a new replacement as once these contacts are damaged, the power to the compressor is somewhat limited and the contacts will weld together again.

  • Miranda Shenoskey

    Over the winter, I took out the fuse unit, in case of an accidental turn on during the winter. Now I am UNABLE to find that unit! Can those be replaced? And if they are how much are they? I’ve looked for hours! I normall kept it in our laundry room and now the box I had it in is completely gone…the picture of where it was supposed to go is attached to this message

  • Rod Fraser

    Last night I heard a noise from my outside a/c central air condenser unit. I went out to take a closer look and the sound appeared to be coming from the fan motor (a slight grinding noise that quickly got louder) I yelled to my girlfriend to turn it off. At that point I did some research and it seemed to be the fan motor (maybe a bearing) and then this morning I turned it back on to take a look again. I was assuming it would make the sound again and I could get a closer look in the daylight. However, the unit has been working all day since I turned it on the first time and hasn’t made any bad noises. It seems to be running smooth and I’m wondering if a fan motor can maybe chew up a bearing or something of that nature and then continue to work well for a length of time before it goes or what could be the situation. I appreciate any advice. Cheers!

    • Don Vandervort, HomeTips

      Sounds like something was loose in there and banging around…let us know if the problem happens again.

  • chris

    I just tightened the belt on my AC and now it doesn’t wanna blow. Is it my motor, I was thinking maybe the motor is no good, it must not be strong enough to spin the belt? I tightened it pretty tight should I lose it? Is it too tight? I should probably buy a new motor right? Any help would be greatly appreciated, please email me if possible thank you.

  • susier

    The wire to contact unit outside got chewed: ac unit does not work. Can i repair wire or reconnect?

    • Don Vandervort, HomeTips

      If the wire is damaged, it should be replaced with one just like it. Be absolutely sure that all power is turned off before replacing the wire. Check it with a voltage meter to make sure it isn’t live.

  • prairiehen2002

    I have a heat pump and my air conditioning will not kick on. The circuit breaker is tripped but when I try to reset it produces a grinding sound at the box and kicks off. I’ve looked for a rest button on the unit but can’t find one. I suspect the condenser is locked up? Any ideas?

    • Don Vandervort, HomeTips

      If turning the circuit back on creates a grinding sound at the electrical box, don’t reset it. Call a professional.

  • Naomi Woods

    Our thermostat is set to 73. Temperature in house is 87. Temp outside is 95. Our landlord has sent several guys out to “fix” the problem, but it is a on going issue. They have installed a new thermostat, checked the cooling fluids in the system, checked the condenser, still the same. They are now trying to tell me that this is normal because of the open floorplan in the living area. The only thing, is that when we moved in two years ago, the unit would cool the area to the point that I would have to wear long sleeves, with the thermostat set to 73. It is using excessive electricity…. my powerbill is now $60.00 past last months billing, and we are only 18 days into the billing cycle. Can someone offer some guidance?

    • Gary McClenny

      Have the landlord call an AC tech. If he will not do it then you call one and have him pay the bill. Several guys are not pros. Call a pro. There are tenant advocacy groups you can call if he gives you any trouble. Your state may also have an agency. This is a breach of your lease.

  • DT

    My condenser is running, outside fan working, but inside blower isn’t running. Turned off the thermostat, and the blower came on, and has been running for 20 minutes. Any ideas?

  • Penny Kuehlman-Diehl

    Outside fan isn’t running. It blows the fuse every time we try to turn it on. The fan isn’t stuck, moves easily when moved by hand.

    • BenHur Dover

      Probably a short in the thermostat wiring. Check each wiring for a short to ground.
      A short can happen when the Thermostat wiring is pinched against the frame when the panels are put back into place.

  • Marilyn Kushay

    Water leak In garag. Last time repairman told me to open small pipe and let water out. I think he told me to put bleach in it. When I let out water overflow, air comes o. And cools for a while.

    • Don Vandervort, HomeTips

      Please see the article above in the section Air Conditioner Leaks Water. Sounds like you need to clean out the condensation drain.

  • BenHur Dover

    Compressor for HVAC Roof Dual Pack has a rhythmic ramping sound. Similar to this:
    Anyone know what the cause could be? When the fan is turned on without AC, the noise goes away.
    Beginning to think that it’s the compressor.

  • Carlos Cosma

    Need help fast!!! I know very little, if nothing at all about HVAC but I pick up things pretty quickly so any help so I can save money here is greatly appreciated. My AC unit quit working. I noticed a buzz last night from the unit. So I went inside to start trouble shooting. Inside temp was 77 and the thermostat was set to 74. The vents were blowing air, obviously not cold, and the unit outside was definitely not running. So I shut off the thermostat, replaced the batteries and gave it another go setting it to 69. Vents started to blow air immediately but again just regular air. AC unit outside will not turn on. All it does is buzz every minute or so as if it wants to turn on but it doesn’t. I can easily reach in with a stick and effortlessly spin the fan (with the power off of course). when the buzzing starts I notice the yellow wire inside actually moves. I don’t know what that means but that’s all I can see for now. I have not taken anything apart as of yet. from the exterior of the unit everything appears to look normal and its obviously still getting power (the buzz). Any ideas?

    • Jeffrey Emhuff

      Did you figure this out? We are having an identical problem!

    • Pablo Bruno

      It’s most likely the capacitor, look up videos on where it is and how to safely remove it and go to a part store and replace it. I had this issue more than once.

      • Don Vandervort, HomeTips

        Yes it is probably the capacitor. Absolutely make sure that you shut off all power to the unit before working on this!



      • Don Vandervort, HomeTips

        Thanks for stepping in to help out with these questions!

      • Gary McClenny

        Actually, the fan motor has a RUN capacitor since it is a split phase motor. If the capacitor goes bad the motor will try to run but will overheat and shut down on thermal overload. The question is—-does the compressor run? It may be more serious than just a fan motor. Also, many times, the fan motor itself will have worn out bearings causing it to overload and thermal out. My opinion is that if the motor is 10 years old, replace the motor and the capacitor.

  • Diane Le Hong

    Hi I don’t know much about stuff . My central air air conditioning isn’t working . Well I can hear it on it blows air but no cold air and the big machine outside fan thing is not spinning . And idea what it could be.



  • James Dugger

    If an installer tried to charge a new compressor with coolant before removing the factory filled nitrogen , would this create any cooling problems? Such is the case with my new 4 ton compressor. Installer can not give me a reason for poor cooling performance. outside temperature 88 degrees. Lowest inside temperature 79 degrees. Seldom shuts off. Would appreciate your thoughts!


      I would call another HVAC guy to find out why.

    • Gary McClenny

      When installing a new unit, it is absolutely essential that a vacuum be pulled on the system before installing refrigerant! Is you contractor licensed?

  • Tim Barnes

    My brother has an ac central air unit. When it turns on, the compressor outside always runs even when the fan inside the house doesn’t. Why?

  • Nebojsa Golic

    My problem is that ac doesn’t cool well, and water is not leaking outside. when i pour it in internal unit it goes out through hose. any ideas?!

    • Dave G.

      The condenser unit outside may need to be cleaned or it is low on freon. Also check the filters on your furnace. If your filters are dirty it can limit the air flow through your evaporator in the furnace limiting it’s cooling ability.

    • Don Vandervort, HomeTips

      Also make sure the condensate drain is working properly. See the article above in the Air Conditioner Leaks Water section for info about this.

  • avenia conley

    my unit wont come on the fan wont blow nothing every time they plug the compressor up it knock the breaker off what do you think is going on need help asap

    • Dave G.

      If the breaker is tripping every time the compressor is turned on you probably have a shorted compressor or a bad capacitor on the compressor. If you’re referring to the condenser unit outside that has the compressor in it, a shorted fan motor in the condenser can also trip the breaker.

  • Melissa butler

    The unit outside is coming on but the inside will not come on just makes a buzzing sound

    • Dave G.

      When you turn the thermostat on, the only thing that comes on in the house is the fan relay and fan. Try switching the thermostat HEAT/COOL switch off. Then switch the fan switch from “AUTO” to on. Only the fan should come on. Now if you hear that buzzing noise you probably have a bad blower (fan) or fan relay. The odds are it’s going to be blower fan.

      • Don Vandervort, HomeTips

        Dave, thanks very much for helping out with these AC questions. Your answers are great!

  • twowarvet

    my ac wont shut off and the thermostat is blank…It didn’t go off when I switched it to OFF. I finally got it to shut down by switching it to HEAT. I think I might need a new thermostat…any ideas?

    • Dave G.

      Yes it sounds like a bad thermostat. The thermostat directly controls the compressor/fan relay in the condenser unit outside. This is the yellow wire connected in the thermostat. When the house calls for cooling the thermostat internally connects the yellow wire to the red wire to turn on the condenser outside.

  • DarthKurt

    My outside AC unit stays on even after the desired temperature is reached, after a while it gets too cold in the house and I have to turn the AC off at the circuit breaker. The Thermostat is fine, works well with furnace and used to work with AC, so I suspect a problem with outside AC unit. Perhaps a relay or Capacitors ? The contact plate looks clean, no corrosion. The unit does work when I turn it on at the breaker, it just won’t turn off automatically.

    • Don Vandervort, HomeTips

      Sounds like a wiring problem. Sometimes wires get “welded” together from heat…or something gets in there that cross-connects them. Or it could be the thermostat. Buying a new thermostat could be the easiest and most affordable first step.

  • Joyce Conley

    brand new unit 3.5 ton for home put in 3 months ago. it works blowing air but not cold and after an hour freezes up outside and inside.

    • Don Vandervort, HomeTips

      Make sure nothing is blocking the air flow either outside (around the compressor) or inside (through the air filters). A kinked refrigerant line, or a blower fan that isn’t running right can cause this, too. Open all registers and make sure nothing is restricting air flow. I recommend calling the HVAC contractor who installed it 3 months ago.

    • Gary McClenny

      The contractor may have never checked refrigerant levels when he installed it, or he may have done a poor job and you have a leak. Call him back.

  • Lucian Simiele

    i turn central on….. it clicks outside in unit… fan doesnt go on nothing? is it the fan motor or condenser?

    • Gary McClenny

      You may have a bad contactor or you may have ants in the contactor. Also, look for any wires that may have burned off where they connect to the contactor. If both the compressor and the fan are not working, check the contactor and also the breaker and/or the disconnect outside.

  • Don Vandervort, HomeTips

    It was iced up and you melted the ice…good job. Now make sure nothing is blocking the air flow either outside (around the
    compressor) or inside (through the air filters). Double check that your filters are clean.

    • Jody

      Thank you Don,
      Since my unit had just been repaired 2 weeks previous to this issue, the company came out the same day I called. They checked it and discovered that it was undercharged. They filled it to the proper level and it has been fine. I was not charged a dime on the repeat visit, because they had initially overcharged it and had to take some out! That left it undercharged which lead to the freezing. That is how it was explained to me anyway. This company was so friendly, understanding and professional that I would recommend them to anyone in the Colorado Springs, CO. Area.
      Rocky Mountain Climate heating and cooling ?

      • Don Vandervort, HomeTips

        Jody, I’m glad to hear you solved the problem—and got it done for free. Cudos to your hvac company.

      • Gary McClenny

        You got lucky! Good job. Yes, low refrigerant will cause the unit to ice up; so will a dirty filter so make sure you change them regularly, like once a month! If you don’t, you will end up with dirt on the evaporator coil and that will cost you!

  • Don Vandervort, HomeTips

    Sounds like the capacitor may need replacement.

  • Don Vandervort, HomeTips

    Make sure nothing is blocking the air flow either outside (around the compressor) or inside (through the air filters). Double check that your filters are clean. Then make sure the condensate drain is working properly. See the article
    above in the Air Conditioner Leaks Water section for info about this.

  • debbie smith

    My ac works but when gets ready to go off seems to power down then immediately kicks back on this will happen a couple times during a cycle any suggestions?

  • Dave G.

    He is correct. The air flow comes from the blower fan in the furance. This blower is used for heating and cooling. Also the outside condenser unit has a separate breaker used to run the compressor and fan in it.

  • Tim

    I have a dual system in a two story house. Up stairs half of the vents have air coming out but the other half, all on the same side on the house, aren’t blowing any air.

    • Don Vandervort, HomeTips

      It sounds like either something is blocking the flow of air through one of the main duct lines before it splits off to individual registers (a damper, perhaps?), or the duct has become disconnected.

  • ron

    my a/c stopped blowing any air at all…the fan is working tho….a guy i know came by & said its probably the blower motor & he showed me that the motor is barely moving but i havent heard from him since….im very strapped for money already but we’re also burning up! what do i do??

    • Don Vandervort, HomeTips

      So the fan in the outside compressor is working but the blower in the inside air handler (furnace cabinet) isn’t? Please clarify.

  • Mayra

    Our air conditioner will leak water sometimes only. It seems like if we put it to low is when it happens. Where do we start to look for the problem first.

    • Don Vandervort, HomeTips

      When the weather is humid, air conditioners can produce a lot of water from condensation. Try to find where the water is coming from…is it a condensation tray or drain?

  • Sherri Luepkes Craig

    I have a double wide mobile home. Last night when I went to bed, I noticed the thermostat said low battery. This morning, I changed the battery, but there only seems to be air coming out of the vents on the left side of the house (same side the unit is on). Is this a problem that can be tied to the thermostat or is it just a coincidence?

    • Don Vandervort, HomeTips

      Normally the thermostat would control the entire system…if it works for part of it, it should be working for all of it.

  • Jim Atkinson

    Hi, thanks for the great troubleshooting tips! I went through the steps you suggest when my AC would not cool. Changed the filter, checked the condensate drains, no water standing, pans dry, pipes dry. Changed the batteries in the T-Stat, unit tried to come on. Indoor fan kicks on, but outdoor fan had a buzz. Pushed the condenser fan a bit and it started. Let it run a bit but still not really cooling. So I am thinking that the condenser fan capacitor is bad, but would that keep the system from cooling as long as the condenser fan is running? Does the capacitor also control the compressor motor? Or do I just need the HVAC Mechanic to check the charge, change the capacitor or two capacitors? System is about 7 years old and has always worked excellent till now. Any thoughts or suggestions would be appreciated. Thanks

    • Don Vandervort, HomeTips

      It sounds like you’ve done about all you can do and, yes, it might be the capacitor. At this point, you should probably call an AC pro (see the links in the article above).

    • Gary McClenny

      If you are handy and know how to use a DMM, you can check the capacitor yourself with the power off and the wires disconnected from the cap. Take a photo first so you can hook it back up. Turn your meter to Ohms and touch the leads to the terminals; the meter should show a rapid change and then stabilize. It should not show open or shorted. Reverse the leads and do it again. The meter should do the same thing. Again, not continuity or open circuits. Look at the capacitors—if the top is bulged, the cap is most likely bad as there is a disconnect inside that opens the circuit when the cap bulges upon failure. An AC tech will charge you about $180 for a new one; you can buy it from Grainger for under $25.

      • Don Vandervort, HomeTips

        Gary, thanks so much for all of the help and expertise that you contribute here!

  • Don Vandervort, HomeTips

    Very true. Thanks!

  • Don Vandervort, HomeTips

    Please see “Air Conditioner Doesn’t Cool Well” above. Be sure your filters are clean and that nothing is obstructing air flow. The refrigerant in the system may need to be recharged.

  • Don Vandervort, HomeTips

    You’ll probably need to bring in an A/C pro to check the unit and, perhaps, recharge the refrigerant.

  • Don Vandervort, HomeTips

    Wow, this could be any of several issues but the bottom line is that something inside the unit (bearings/motor/etc.) is probably going to need to be replaced by a pro. See the links above to get a local pro.

  • Don Vandervort, HomeTips

    If you paid an A/C guy to fix your A/C 5 days ago, call him and tell him it hasn’t been working right since his visit. Regarding the leak sealant…I’m not sure what he is referring to…is the refrigerant tubing leaking?

  • Sammy

    Hi! Thanks and here’s my similar dilemma…

    I came from Gulf Coast oceanfront, where a new central AC worked in a dandy duet with a separate central dehumidifying system. I wanted this again at in my new little condo I’m renovating that’s across the street from the Pacific in North San Diego county. I chose a reputable vendor with sensational references. He urged I just stick with a small BTU central air unit for this little condo, forget April Aire and for sure get a UV Light Air Filter scrubber in my new system. (I have allergies.)

    Things were working great! Until water started leaking down into the underground garage from the concrete’s seam in the proximity of my new indoor AC unit. Suspicious-looking: bright green hardened droplets coming out of the seam and from which the water would drip to the garage floor.

    Refrigerant leak?

    I shut off the system. Checked the air filter. Wow! In less than 2 weeks — shaggier than a buffalo! And we were only in the painting/finishing stage of the renovation!

    I won’t get tedious…but this happened again…except the air filter was FINE. I opened the closet housing the AC. A thin film of MILDEW had grown! Condensation was on the sides of the unit with puddling water standing on the flat surfaces! My AC pro is flabbergasted. Says he’s “never had anything like this happen.” He’s been doing oceanfront/high humidity homes for years.

    If ONLY I had purchased a home warranty with AC. I did not. I was not sure I was going to install it this close to the ocean. CAVEAT EMPTOR — but be sure to buy AC on that home warranty regardless, y’all!

    Next: my insurance company perform an estimate. I was reassured there was NO penalty in doing this. But I have a $1,000 deductible and this event will likely make my premium go up $500. My vendor says the labor will be $500, but he’s going to have to tear out some old drywall and a new closet interior treatment.

    the city signed off on this installation, too. I had a permit.

    I’m bumming. I like the guy! His reference are stellar. But is this a “Perfect Storm” this time? Will I have to sue him? The faulty install could be a messed-up decision on the trap and now I’m concerned prolonged water trickling has compromised the BRAND NEW TRANE system!

    THOUGHTS!??! Thanks for you help.

  • Kimberly – O – H – I – O

    My Payne unit quit working. It engages but was not starting. The fan on the exterior unit was humming but not going. I used a stick to give it a start and then it worked. The fan doesn’t seem to be moving fast fast, then again I never noticed how fast it should run. I hear what I assume is the compressor trying to ‘tick’ into engaging but it doesn’t start. All I hear is the fan motor. If the fan is failing and not running like it should, could that be what is preventing the compressor from starting? It seems surprising that the fan and compressor would both stop working at the same time. Before the problem, I never had any issues and the cooling was always pretty cool so I think my coolant level is ok. Anyone have any ideas that I could try for DIY. I am the handywoman around the house, I live alone! I no way can afford a pro and would just have to go without unless it’s an inexpensive fix! ANY SUGGESTIONS?? Please and thank you!

    • Gary McClenny

      See my suggestions above about ants in the contactor. Always turn off the power before checking any electrical.

    • Gary McClenny

      Kimberly—-for your safety, please do not advertise that you live alone. I am a former police officer and can tell you many horror stories about that. I am happy to read that you are the handy person at your house and are willing to learn and perform those tasks! Congratulations. I live in Texas but sometimes work in Chillicothe, OH at the VA center there. Good luck with your unit.

  • Curtis

    High pressure line is sweating at the start. Getting some cool,but concerned that the high side is cold.

    • Gary McClenny

      High side does not sweat. The small line is the high side; the large line is the low side. Low side line sweats.

  • ali

    my ac stop working yesterday checked the vent the fan is on but no cold air checked the ac unit outside it wass not turned on ckecked the breakers all ok can u suggest possible problem

    • Gary McClenny

      Some units have a fuse box or breaker box outside. Check those first. Sometimes, ants get into the contactor and block the contacts from closing. Look for ants and signs of ants. They can be really bad about that. If none of that is it, call a pro. You may have more serious issues.

  • Becky

    The ac is working great but, as I was cleaning out the registers I noticed water down inside the ducts. Never noticed this before. Is this a problem?

    • Don Vandervort, HomeTips

      If hot air is leaking into the air duct, condensation can form. Or, the duct may be undersized for the air flow. Either way, you should probably have an AC pro check this so that you don’t end up with problems of mildew or mold. See the links in the article above to find a pro.

    • Gary McClenny

      Make sure the ducts and the register boxes are insulated. Ducts are like a glass of iced tea sitting on the table. The outside of the glass gets wet from condensation. The ducts do the same thing and sometimes drip water if they are not properly insulated.

  • Tish

    I have a split level house ,the lowest level is very cold ,while the bedrooms upstairs are uncomfortably warm. Any tricks ,I already closed off dampers ?

    • Don Vandervort, HomeTips

      Do everything possible to minimize the amount of heat getting into the house, and then try using fans (and turn on the fan switch on the thermostat) to keep the air moving from upstairs to downstairs—presuming that there is at least one “cold air return” register upstairs.

  • Don Vandervort, HomeTips

    It sounds like the fan switch in the thermostat needs to be turned to “Off.” See if that works.

  • Don Vandervort, HomeTips

    Is it the fan in the air handler (inside) or the compressor (outside) that isn’t turning? Also, which part is humming?

  • Don Vandervort, HomeTips

    If air is coming out of the registers upstairs but it isn’t cold, first try the steps in the section “Air Conditioner Doesn’t Cool Well” above. Be sure nothing is blocking air flow (clean filters, clean compressor coils). You used the plural term “compressors,” so you probably have a dual system. One of them may need to be recharged with refrigerant. You’ll need to get a pro for that. See the links in the article above to find a pro.

  • Gusty Rheni

    I replaced the compressor and the fan isn’t working still? Also the vents are blowing air and I turned the ac off any suggestions?

    • Don Vandervort, HomeTips

      Are you referring to the fan in the compressor? If so, it sounds like it isn’t getting power. The vents will blow air with the ac off when the “fan” setting is turned on in the thermostat.

  • Manzurul Kabir Nipu

    My air conditioner indoor unit fan runs correctly but its not blow much strong air on on the left side. Some times air flow from fan increase and decrease continuously. What is the problem actually? Can you help me out?

  • Mario

    I cleaned my central air unit removed cover it ran good for 15 min. was cooling good then stop ! I removed the breaks insert them back in fan start to move slowly then stop and just had a humming sound ?

  • John

    The outside compressor unit’s fan was stopped but there was a loud hum coming from it. I shut the system off and about 16 hours later I turned the it back on and it worked fine and has been working well ever since. Strange!?

    • Gary McClenny

      You may need a capacitor for the outdoor fan unit, but most likely you really need to replace the outdoor fan motor. It is not hard to do but be sure to turn off the power before you do it. The motor is less than a hundred bucks; you can get it at Grainger if you do not have any other source. Once installed, make sure it is turning the right way—if backwards, look at the wiring diagram on the side of the motor and it will tell you which wires to change.

  • Lynne Stimac-Rhoades

    My hose that goes from my air conditioner to my house is freezing up…..what does that mean?

    • Don Vandervort, HomeTips

      This can happen if air flow is restricted by dirty filters, blocked vents, dirty coils, etc.

  • Don Vandervort, HomeTips

    Note in the “Air Conditioner Leaks Water” section above that some condensate pumps will shut off the system if the pump isn’t working (shown in left photo). The stand-alone condensate pump shown in the right photo is about $50 and you can buy it by clicking on the photo. And, yes, there is a relationship between the pump and the system…the system may not cool effectively if the condensate drain is plugged.

  • michael

    My central air conditioner unit is not making any condensation. I know it should make several gallons per day so it has me a little worried. Is there a specific problem that would cause this?

  • Gene Boerner

    I have 2 central air units. They are working fine. I decided to go up to the attic where the air handling units and evaporator coils are located, to make sure the condensate drain pans looked OK. One unit, the smaller one, has water in the drain pan and the overflow goes to outside like it is supposed to. The main unit, however, which runs a lot here in Oklahoma summer weather, has an absolutely dry drain pan. Where is the condensate going?

  • Gary McClenny

    Most likely your indoor coil (the evaporator coil) is dirty. Even with filters, some dirt and animal hair gets past the filter and eventually stops some of the airflow. Reduced airflow whether it is caused by a dirty filter, dirty coil, dirty squirrel cage blower, or bad fan motor will cause the coil to freeze up blocking the airflow completely. If all that is correct, you need to call a pro to check the refrigerant level. There are only two things that cause a unit to freeze up; they are reduced airflow over the indoor coil and low refrigerant. If the refrigerant is low, you may have a leak.

    • Don Vandervort, HomeTips

      Gary, thanks very much for weighing-in on this. We really appreciate your help and your expert advice!

  • Gary McClenny

    Air should never come out of the return! If air is coming out of the system, listen to your unit inside to see if the fan is running. If it is not running, you may have a hole in a duct and outside air is blowing into the system.

  • Gary McClenny

    Upstairs are harder to cool. The units are generally sized by square footage and upstairs are usually smaller than downstairs so they get the smaller A/C unit. That can be tragic since in southern climates (not sure where you are) the upstairs can get brutally hot and the unit will not cool it down. First, check to make sure the upstairs unit is actually running—not just the outside unit, but the inside unit as well. Then, check the ducts to make sure they are insulated and the insulation has not fallen off (if they are metal ducts). Feel the air coming out of the registers and use a thermometer if you have one to see what the air temperature is. Make sure the filter is clean. Other than that, you may need professional help.

    • Don Vandervort, HomeTips

      Great advice. Thanks, Gary.

  • Gary McClenny

    You are low on refrigerant—-again! Low refrigerant will cause the indoor coil to freeze and you will not feel air blowing from the vents and the house will not cool. Call him back out to check the refrigerant.

  • Gary McClenny

    I agree with Don, especially about the airflow. You may need to get the inside coils cleaned.

  • Gary McClenny

    Quick check is to touch the red T-stat wire to the green wire. The inside fan motor should run; if it does not, the transformer in the blower unit is bad or a rat chewed the wire!

  • Gary McClenny

    I agree with Don that the capacitor will cause that problem, but if the unit is more than 10 years old, you may need a new outdoor fan motor as well.

  • jr61020

    instead of buying a new Electric Condensation unit can I just route a hose from the water supply to a drain and remove the unit altogether. If so will the AC still work

    • Don Vandervort, HomeTips

      Pumps are needed where the condensate drain water can’t be carried by gravity so, yes, you can just run a hose from the condensate collector to a drain as long as it only goes “downhill.”

  • disqus_cxl3q5yHIX

    Central A/C runs but does not cool. New filter put in just now, cleared water pipe, did all that was listed except call repair might need freon or what ever. Has been 21 years since installed.

  • jr61020

    Thank you for answering my question about the Air cond and hose

    • Don Vandervort, HomeTips

      My pleasure, please return to HomeTips often!

  • Don Vandervort, HomeTips

    Gary, correct me if I’m wrong, but it sounds like there might be a blockage. Curtis, try to see inside the unit to find where the ice starts to occur—maybe right after an in-line filter.

  • txcarp

    Hi Don and everyone- thanks a million for all the helpful info! It helped me eliminate what the problem is not, but I still don’t know exactly what it is. Brief description of the issue that started yesterday:
    Thermostat set at 75 seems to be working exactly like it should and switches on the compressor and fan, but the fan shuts itself off after only 26 seconds each cycle while the compressor keeps running. Then the fan kicks on again a few minutes later for another 26 seconds and quits again. The house temp is about 83, so it seems like the compressor is getting the message to keep cooling from the thermostat, but something is telling the blower motor to stop. The capacitor is good- tested with a meter- and I bypassed the t-stat and got the exact same result, so I know it’s not that either.

    So, seems like that leaves either the blower motor or the board. I’m guessing the board, because the blower switches on when it should and has not tripped any breakers or fuses – it’s just getting a signal to shut off from somewhere (prob the board). The blower does the same exact thing when the cooling switch on the thermostat is off and just the fan is switched on- 26 second run cycles every few minutes. When the thermostat is switched to cool, I can hear and feel the coolant cycling through the high pressure side before the blower kicks on. Is this a sign that there is air in the system and not enough coolant? Could that be the problem? It’s an older system from 1999.

    It’s supposed to be over 100 here the next few days, so any info or direction would be very much appreciated! Thanks!

  • Chi Amanda Renfrow

    My ac froze up a couple times this summer and I cleaned the filters which seemed to work but today I turned it on and it sounds like it’s running fine then it sounds as if it shuts downs then cycles back on again then shuts down again (I turned it off at that point)

  • Willis Swanstrom

    The air coditioner works well all day except for once or twice a day it makes a lound vibration noise. I turn it off and restart it and it sound alrigt. It’s so loud that it vibrates the house wall next to it. What’s wrong?

    • Robert Young

      Our unit, a Lennox , was installed a year ago . When the ac turns on it sounds as if a small bomb has exploded. The unit installer says this is normal. Is it?

  • Darlene Matthews Chandler

    AC motor runs but only blows cool air if fan on thermostat control inside is turned on continuously. Any suggestions?

    • Don Vandervort, HomeTips

      Hmmm…check the wiring of the thermostat. You can probably get specifics by searching the make and model of the thermostat online.

  • Bill Brown

    When my ac is turned on it starts fine – cool air starts to flow – but then the outside fan starts to slow down and comes to a slightly squeaky stop. Then the motor just whines until turned off. Could it be the bearings?

    • Don Vandervort, HomeTips

      Definitely sounds like the bearings. Too much friction. When it overheats, it triggers a thermal shutoff switch. You probably need to replace the motor…and maybe the capacitor.

  • Cheryl Haupt

    I have a Tempstar 2 1/2 ton a/c. The compressor fan motor went out. I live in Houston and cant go without a/c. The tech replaced the fan motor (a universal, since my unit is discontinued) and the capacitor. I was charged $695.00. I feel like I was over charged. Can you tell me if this seems like a fair price to you? Thanks for your time and look forward to your reply.

    • Don Vandervort, HomeTips

      Cheryl, unfortunately that is in the ballpark of averages, particularly in a busy AC season. For parts and labor, the motor typically costs from $300 to $500 and the capacitor from $150 to 300. It’s always best to get an estimate before the repair person starts…but I know you’re already invested by the time they come out to the house.

  • Lmyersl86

    any reasons a central air fan would stop running intermittently and won”t t run until the fan is spun manually?

    • Amy Taylor

      yes, that means you need to replace the capacitor. Very easy and cheap fix. You can youtube how to change. It takes 5 mins to do.

      • Don Vandervort, HomeTips

        Amy, thanks for helping out. Good advice!

  • sky

    blower in the heat ex-changer sometimes will not start. Outside pump is running. Shut the system off and re-start and the blower starts. Relay or maybe capacitor??

  • Michael Adams

    I have changed out the capacitor and contact switch. The fan turn on when I push the reset switch in but then it turns off again. I thought the old contact switch was bad but it is still doing the same thing with the new contact switch.

  • Dennis

    my automatic condensate pump is not working and is hot and it smells like a burned transformer. says it has safety switch. where is it and can I reset?. My whole furnace and a/c won’t work?

  • Russ Hanna

    Earlier today I moved some things over by the air handler and something knocked the drain pipe loose. There was water around the base of it which happens to be galvanized to the floor. Nothing is working, air condenser, air handler or thermostat. Breakers and and fuzes aren’t blown or tripped, yet nothing is working. I’ve turned all off for the suggested 2 minutes, nothing; and also manually did the Y to R contact for over 2 minutes. Older thermo with 5-7 wires connected in one way or another. No resolve as of yet, could it be possible that the puddle caused it to arc out after making ground contact because of the water puddling around and under the air handler? Please help, I’m in a sticky situation as we have another week before we move due to foreclosure process blind siding us from landlords lack of paying mortgage payment for years. He’s dropped all responsibility and the bank will step in on oct 8th. We’ve got 4 more days before moving to the new rental we have secured. Meanwhile my wife and I take care of a 50 yr old mentally handicapped and it is an issue jeopardizing our legal guardianship of her. I need educted advice for a temp fix for the next 4 days at the least. Please!! I am begging for help here. I can’t find my hot wire tester (tig tester) so this is quite difficult as it is without knowing whether or not there’s power there to single out a problem internally. Or if the power isn’t present which means that’s the entire issue in itself.

    • TJMaximinimonious

      Sure it was a drain pipe and not a cooling line?

      • Pat McBride

        You would definitely know if it was a refrigerant line.

  • Amy

    When we get a heavy rain, the a/c unit makes a loud noise when it runs. Almost like a thumping sound and you can hear water. The noise comes from where the filter goes. Any ideas?

  • Jonathan SirKnight Bladen

    Whenever my unit kicks on, it temporarily knocks my modem and a couple other devices out. Believe it is drawing too much power, but don’t know why.

    • Don Vandervort, HomeTips

      Is your modem plugged into the same circuit that powers the AC? If so, you need to plug it in to a different circuit or consider getting an uninterruptible power supply (UPS). AC units draw a lot of power and this surge is enough to mess up electronic gear.

    • OldTooly

      Please check you ground. Check everywhere beginning at your service box and then at each receptacle or junction for all the lines powering the devices in question. Quick test, put a light bulb (old school bulb not a CCF or LED) into the power socket powering the modem. Turn on A/C and note if the bulb changes intensity. It should not vary much at all. Either brightening or dimming indicates a problem. Strangely enough the brightening usually means the ground is at fault. Dimming can also mean poor connections or damaged wiring, but as you have suspected, it can also be a worn compressor drawing too many amperes. Perhaps there is a professional here who can elaborate more completely on this issue. P.S . ALuminum ground wires are quite often the culprit since they corrode at connection points or anywhere weather or moisture can come in contact. Good luck and follow all safety rules and common sense.

  • Janice

    I’ve never been on one of these chat places before so please bare with me. I am alone here in Florida and moved into an apartment. Soon after moving in my apartment became very damp and cold the air soon after begin to smell musty and within a few days it was very uncomfortable to be sitting here in the apartment. I went to the apartment manager and he send a technician over who said there was nothing wrong. Soon after that I got down on the floor to find out my rug was very damp I went out and bought a basement size dehumidifier within hours the bucket was full and this continues to be a daily issue. I have approached management on several occasions and they throw up their hands and say all the tests are normal and they don’t know what to do if anything. I also want to add that the water coming out of the bucket from the dehumidifier has a smell to it which I can’t identify. Does anybody have an idea as to what the problem might be I am NOT going to let this drop and will keep pursuing it but I’d like some kind of an idea if anybody has had this issue what they did to resolve it.

    • Don Vandervort, HomeTips

      Is your apartment floor at the bottom of the building—on a concrete slab?

    • Janice

      Yes it is. I have a neighbor right next to me and she is not having the problem I have and our apartments are connected

  • Don Vandervort, HomeTips

    Hi Jerry, thanks for commenting. You’re right that you can buy a capacitor for very little. I was referring to the average costs for parts and labor—the latter being by far the most expensive, particularly in the height of the season, as you point out.

  • Joan

    I was replacing a filter in the inside Handler and the filter was wet. In searching most often is said the drain is plugged. My drain from the handler goes into the floor. I poor vinegar into the upper part of pipe regularly. Today I used hose and sent water down the seemed to go ok. I went outside and by the compressor is a pipe. This is often mentioned in what I have read to be the drain, but I have the floor drain. Nothing came out this pipe when I used hose. Also read about vents. Could this be a vent to my washer??? All very confusing….

  • Micah

    When I switch my thermostat from cool to heat, it blows the fuse in the air handler. Please help!!

  • I have a “gas pack” in NC. Last night we noticed the house was not cooling to the set temperature and it was starting to warm up again outside. First thing I checked was the floor vents to make sure air was blowing. It was not. Went outside and the condensing unit was running but the compressor was freezing up. I thought it might be a belt on the blower motor. So I shut the unit off for the night. Woke up this morning and turned it back on. Darn thing started working just fine. How is it that the blower was not working, the compressor was freezing up, but today it is all working as it supposed to? Makes no sense to me. I’m sure it didn’t fix itself and the problem will likely pop back up again. Suggestions?

  • Robert

    My heater worked great last winter but this winter it won’t kick on.
    I do not have the old style pilot light and my central air unit ac side works great and blower fan works great also.
    When I turn up thermostat I hear a click,then a hum but no ignition or fire burning so I think my ignition has went out.
    How do you I check and or replace ignition?
    It’s a 1997 Coleman heater ac unit propane.
    Any suggestions?It has a window to see fire but there is no fire of sparks that I can see when thermostat is turned up.
    Thermostat works on ac and I cleaned and checked all the contacts on thermostat,so I think thermostat is fine.

  • Joey Watson

    Outside unit is kicking on and off at 7 second intervals.

    • Don Vandervort, HomeTips

      Short cycling may be caused by an improper thermostat heat anticipator setting (see Thermostat Repairs at, a refrigerant leak or improper charge, by icing over of the evaporator coil, a malfunctioning control board or a couple of other things. If it isn’t the thermostat, you’ll probably need a pro to resolve this.

      • Pat McBride

        Improper filter maintenance by not keeping it cleaned can cause dirt and debris to bypass the filter and block air flow through the coil. Another possible cause for short cycling, and icing of the suction line coming our of the air handler.

  • National AC contract replaced my evaporator coil because they said it was falling apart and clogging the drain (unit is 3.5 years old) when they pulled the evaporator and box out of the attic it had a little rust on the coil end supports but everything all the remaining aluminum looked good. Did i just get taken? If so what recourse do I have?

    • Don Vandervort, HomeTips

      Sounds strange to me. The unit should last a lot longer than 3.5 years. Why was the evaporator coil falling apart?

  • Trent B

    Got a head scratcher. A couple of days ago I tried to start my AC…unit was turning on and blowing air but outside fan would not run. I cleaned coils and replaced capacitor last night but when I turned power back on and tried to start up, the AC unit in attic (that was previously working fine and blowing air) would not come on. Checked power at panel and tried resetting several times. I even went back to the old cap to ensure it had nothing to do with the new equip I installed but still no luck. I have since put the new cap back on but have no idea what to check from here. Note–on the furnace in the attic there is a switch that must be engaged for unit to start. It usually clicks when engaged whether it starts or not. The switch will now not click at all. I tried bypassing the switch with jumper wire but still no luck. Any suggestions would be greatly appreciated. At this point I’m not even sure if the first problem was solved. I could still have a bad fan motor and a bigger problem on top of it all. Thanks in advance!

    • Don Vandervort, HomeTips

      Trent, it sounds like the power has been interrupted somewhere…loose wire, bad switch…etc. I hope we can get an HVAC pro to weigh-in on this problem because there are so many variables.

    • Pat McBride

      Sounds to me like in the process of replacing the capacitor, you moved or disconnected a low voltage wire that runs the air handler. You did not say whether the compressor was running, and the fan not running in the outside unit. If the run capacitor was faulty, you should have heard the fan humming.

      • Don Vandervort, HomeTips

        Pat, thanks very much for helping our community!

  • Don Vandervort, HomeTips

    Make sure the main circuit breaker and service switch by the unit are both on. Beyond this, there are other safety switches in the unit (high and low pressure safety switches, motor overload reset, etc.) that may have switched off. If you’re not familiar with this type of equipment, please call a pro.

    • Pat McBride

      Did you turn the service valves back on to pressurize the system?

  • Alicia T

    Yesterday I noticed that my fan will stay on when my AC is off. I have shut off unit completely so I don’t burn out the motor. Any suggestions as to why this suddenly started happening? And what can I do about it. Any help will be greatly appreciated. Thank you

    • Pat McBride

      The contacts could be welded together keeping the fan running, but not the compressor. Replacing the contactor or gently pry the contacts apart will probably fix it. A new contactor would be best.

      Make sure you turn the power off before messing with the relay/contactor

      • Alicia T

        Thank you very much for responding..I am wondering why this would just start happening…Do the the contacts sometimes move together by themselves? It was working perfectly before…I will try your suggestion..thank you again…Have a nice day!!!

        • Pat McBride

          They arc when making or breaking. As the wear increases, so does the resistance, thus increased arcing as well. Return springs wear out to the point that they don’t open the contactor fast enough to prevent prolonged arcing. Just a few causes and when the welding occurs, it’s instantaneous without any warning.

          • Don Vandervort, HomeTips

            This is an awesome answer!

  • Scott

    So my first posted question disappeared. I have two central a/c units, one cools the upstairs and one the downstairs. The upstairs a/c unit is the smaller of the two. This is the one that has the problem. The a/c unit cools the upstairs as it should. Cycles as required on temp. The problem I have is when the temp is reached and the thermostat kicks the a/c unit off outside, there is still a him coming from the outside unit. If I switch the thermostat to the off position, the humming goes away. If I switch it back to cool, it starts humming again. Any thoughts what could be wrong and what to check?

    • Pat McBride

      The humming could be the low voltage transformer, it the outside unit is also the air handler. Otherwise it probably does not have a transformer on the outside unit. That is the only device that has power to it when it is not cooling. Just guessing as I’m not there to meter the unit.

      • Don Vandervort, HomeTips

        Pat, Thanks VERY much for weighing in with your professional answers! It’s really great having an expert HVAC guy like you helping out our community!

  • Rice

    My outside unit won’t come on. I had someone check the capacitor and it was fine. If I push the shunt in on the contact in the outside unit it will start. It just won’t hold. I checked that contactor but I didn’t get the 24 V on the low voltage side coming in. Where do I go from there as far as checks on the low voltage side. How do I check the transformer and everything else?

    • Pat McBride

      did you check the door switch on the furnace? Could be a transformer issue, but if the inside air handler, (furnace blower) comes on, then it’s not the transformer. Then check the thermostat settings, and the stat.

  • Annamarie Gardner

    My a/c was running today, and it made a popping sound, and when i took the front panel off the a/c and furnace unit and it had some water inside. what might cause that

  • Chris

    I had my AC running for almost 5 years and until today it is in good condition. Thank you for this wonderful article.

    • Don Vandervort, HomeTips

      Thanks for visiting HomeTips—and thanks to our community members like Pat McBride who come in and help answer questions with their expertise!

  • Arrionana Johnson

    Today my ac turns on and you feel the air but it doesn’t get cold could it have over heated it was working fine yesterday any suggestions on what it could be plus it makes an ugly noise when I turn it on or off and I already changed the filter for it

    • Pat McBride

      Not much information to go on, but It sounds like your fan in the condenser, (The outside unit), could be the problem. You need to tell us where the ugly noise is coming from to help you.

  • Don Vandervort, HomeTips

    Roger, thanks very much for this! We will add it to our article. Please come back to our community here at HomeTips often!

  • Pres.

    My air handler is new as of last year and my outside condenser is in pretty good shape. The vents inside the house are shooting out cool air with a force to move your hair, but two things: it is not circulating well throughout the house, and the temperature is constantly fluctuating between 78-85 degrees when the thermostat is set to 74. It never even gets close to that temperature. Additionally, the refrigerant line is leaking non-stop. I was pretty sure it was condensation at first, but come on, 3 bowls daily to empty out or it’ll overflow? Is there something wrong with the refrigerant line? Could that be the cause of the improper circulation and lack of cooling?

  • Don Vandervort, HomeTips

    Pat, all questions get posted and we haven’t had an expert like you on the site to help answer them. Your answers here have made a tremendous difference in helping people WHEN they need the assistance. But also know that many visitors have the same questions, so your answers are helping people now and in the future. Thank you!

    • Pat McBride

      Thanks for that explanation Don. I understand your meaning and agree.. And with my love of the trade, I feel good in exercising my past skills, and to help folks out. There are a lot of people that cannot afford the high cost of techs and have the skills to make some repairs themselves. And those that just want to be able to make their own repair. I was always one of those. I don’t intend to take food from the folks that make a living in HVAC. But still there are those that cannot afford a service call.Also those that get taken advantage of by shady repairmen.
      Thanks Don.

  • Pat McBride

    The small line from the outside unit, (the condenser) should be warm. If the house is very warm, the line will possibly even be a bit hot. The larger line, (the evaporator line) should be cold to the point to where you feel “flashing” very cold. And this line should be sweating. If you don’t have this condition when the house is close to desired temp, then you could be low on refrigerant.
    The discharge air coming out of the closest vent to the air handler should be about 18 to 20 degrees colder than the ambient air temperature in the house. Any higher or lower than that indicates an issue either with a low charge or air blockage in the condenser or the air handler. Too low discharge temp indicates low air flow through the air handler, and higher temp may indicate a low refrigerant charge. Open up the air handler and check for a clean coil, and loose fan belts not moving enough air. Also look at the squirrel cage fan blades for dirt build up.Good luck

  • Bhai

    My A/C not cooling the house. i had a technician come onsite and have him verified. he said nothign wrong with the system and enough coolant there in, however he said there could be blockage. he suggested me to contact manufacturer. can you please suggest what is this blackage could be ? and how can i fix it. i tried to reach manufacturer but no help.

    • Don Vandervort, HomeTips

      It’s strange to me that a technician would come out to the house, check the system, and leave without diagnosing the problem or faulty part and without being very specific about what needs to be replaced. Does the system run but not blow cold air? Does it blow any air at all?

      • Bhai

        it blows air but the as usual as it does. technician touch the freon pipe out side and said it is cold and did the same at the other end of the inside unit and said it is not cool. so he concluded that there is a major block and he cant do anything and advised me to contact the specific company who deals with this kind of model( payne)

        • Pat McBride

          That is good advice. You need a technician that will get deeper into the problem and the dealer of that brand will be more experienced.

  • Edwin Pinero

    the motor fan in the attic doesn’t come on often. I change the capacitor and it worked for a few days then the compressor is still on and the line leading to the house is frozen. what can i do to correct this continuing problem.

    • Pat McBride

      Sounds like a possible defective fan contactor or a damaged fan motor. You need a service tech. Again, a frozen line to the compressor will eventually do a lot of damage. Much cheaper to fix it now than to replace a compressor.

  • Mike

    Hello, we recently moved to a new house (2 floors), we have two AC units, in the bottom floor the AC works fine, however on the top floor it is a mess, during the day the temperature stays around 80 degrees never goes below 79 (we set the AC to be 75 but it never makes a difference), the compressor and the fan are working, and there is cool air coming out from the vents, however the AC is never able to cool down the top floor below 79. at night we set it to 78 and it is fine in 2 bed rooms, however there is also another problem, in the master bedroom it is cooler there, in the other rooms it varies between ‘ok’ and boiling hot. the filters are brand new btw. usually the AC stays on all day cuz it never reaches the desired temperature. i would appreciate any help here, thank you !

    • Don Vandervort, HomeTips

      Mike, this is not an unusual problem. Because heat rises, all the hot downstairs air is rising to the upstairs and overworking the system, which may be undersized. In addition, your attic may be under-insulated. Is there much air flow in the rooms that don’t cool well? If not, try to check the ductwork for dampers that may be partially-closed , restricting flow. If there is plenty of air coming out of the registers but it isn’t cold, I’m going to guess that those rooms are pretty far from the air handler and that the ducts may not be insulated. Maybe they pass through the hot attic, where the cold air gets warmed. Does that make sense? Insulating the ducts may help. I think you’re probably going to need to get an HVAC person in there to check out the system.

      • Mike

        thank you for your reply, yes what you said makes sense, let me answer some of your questions to make it more clear, in the master bedroom the airflow is strong and cold, the room is usually cool, in the other 3 rooms it varies, the airflow gets less and less, for the room above the garage it is usually very hot, and actually in the upstairs bathroom (not the master) there is barely any airflow and the bathroom is usually very hot. So i think like you said the problem is either with the attic, or the dampers. if you have any more suggestions let me know, the rooms are very close to one another btw. i will surely need to get the AC checked by someone. thank you

        • Don Vandervort, HomeTips

          Yes, Mike, it sounds a bit like maybe some of these rooms were part of an add-on (above the garage, maybe?) and that original ductwork that was meant to serve 2 or 3 rooms now serves all of them. By the time the air gets to the far end, there’s nothing left. You can try using the register baffles to slow delivery at the front end, but that may not help much. A system of zoned heating dampers might help, depending upon the ductwork configuration. See for more about this.

    • john


      I have same issue with AC in my home.Bottom floor works fine and top floor has issue day time.
      Top floor temp raising to 80 during day time though I set for 72 and no Issue during night time.

      What did you figure out with your top floor AC ?

    • Pat McBride

      I am curious as to the location of your return air in the upper part. The room you say is cooler may be where the return air duct is located and just pulls the heat out of that room and not so much the others. Return air placement in a two story home is very critical, and some home builders my take a short in put them in the most affordable place. Keep it in mind that hot air rises and cool air falls so the down stairs unit should not be working hard at all.

  • Don Vandervort, HomeTips

    Please see “Air Conditioner Does Not Cool Well” in the article above. Other possibilities are that the condensate drain is clogged or the thermostat isn’t working right. Or, if the system is pretty old, the refrigerant may need to be recharged—something a pro must do.

  • Lynda Silvis

    We have an older central Heat Air Conditioning system. When we turned it on this year it ran a couple of days then quit cooling. We open up the inside unit and discovered that the A/C coils(?) were frozen over. We thawed everything, replaced both the filters, and swept out the upper unit. We turned the unit back on and it worked another couple of days and the same thing has happened. The A/C coils (?) were again frozen over. Any suggestions as we are financially unable to replace the unit at this time and we live in south texas so really need some kind of cool air. Thanks a lot for any help

    • Pat McBride

      Sounds like it’s low on refrigerant. Another possibility is that is not moving enough air across the cooling coil. Ex. dirty blower wheel blades, or worn fan belts, it they exist. You say you swept out the upper unit, so I take that as meaning you can get access to down flow side of the cooling coil. You probably need a service tech. It’s not healthy on the compressor to send un-boiled refrigerant back.

  • Ryan Matthew Hebert

    We just moved into our new home tonight to find some sort of problem with the ac. The home has been vacant for about 9 months for a remodel. when we moved in tonight I tried to turn on AC and we got a little bit of air (not very cold) coming out of the vents. All of the breakers are good, and everything’s fine as long as I can tell. The outdoor unit almost doesn’t seem to have any power going to it and the fan doesn’t spin. I tried turning it to “kick start” but it still doesn’t work. It’s about 85 inside and really really humid. Please help!?

    • Don Vandervort, HomeTips

      Ryan, the outdoor unit is probably connected to its own electrical sub-panel box with a breaker (sometimes a handle). Make sure it is powered on.

  • Don Vandervort, HomeTips

    ChiChi, by the beginning of your post, it sounds like you have a faulty thermostat. Are you SURE it doesn’t have batteries? Considering the urgency, if I were you, I’d be tempted to buy a replacement …and see if the AC guy will cover the cost when he returns. I don’t know what to make of the last part of your post.

  • Don Vandervort, HomeTips

    Are you saying that it keeps tripping its circuit breaker? If so, it could indicate an electrical problem that should be looked at by a pro. But first make sure the unit has good air flow—clean or replace filters, etc.

    • ZA

      Thank you for your answer. We did replace the filters. It worked longer but then it happened again. We will check for electrical problem.

  • Bryan Seibt

    Is there some sort of low air-flow safety switch to prevent the fan from coming on? (I need to replace the filters.) The outside unit runs and moves coolant into the coils but the fan is not coming on. Even when I turn the heat/cool to off and the fan from auto to run, there is no run. Any ideas?

    • Pat McBride

      Check for a door switch on the air handler. If the door is not shut correctly, it will not allow the fan to run.

  • Pat McBride

    The run capacitor is not working. It’s a canister that should be near or on the fan motor. Replace it and should be ok. Do it soon or the motor will be damaged.

  • Linda Milliken

    I have a Revolv air conditioner. This started after winter when days were hot and nights cold. We would switch from heat to AC, but it wouldnt come on. We would have to throw the breaker and wait a few minutes then turn breaker back on and air would run. The power went out the other night and when it came back on it felt as if the heat was running. We threw breaker and back on and air ran. Few days later and now air runs all day then starts blowing hot air, but throwing breaker doesn’t fix. AC repairman unhooked heat and straight wired but last night started blowing hot air again after being cold all day. What can it be?

  • AmyG

    What is the problem if it seems like everything is running except no cold air coming out of vents inside? And we just used it earlier in the week and worked fine….

    • Don Vandervort, HomeTips

      Please read “Air Conditioner Doesn’t Cool Well” above and let me know what you have or have not done. Need more info.

  • Clinton Lewis

    My apartment air conditioner has never cooled like it is supposed to. it has been on most of the day, today, and I am sitting here typing this sweating. I’ve called the landlord, and they’ve sent someone, but every single time. “Oh the room won’t cool because your curtains arent blocking the sun in the living room properly”, or “the compressor was bad, I replaced it” you can replace a compressor in 30 minutes? “you’ve got full levels of Freon”, and at that particular moment, it was blowing cold air. hour later it’s 80 degrees in my apartment. I feel like my landlord wants me to move so he can raise the rent higher for a new tenant, I can’t really afford this as I am also a caretaker fr my aging grandmother. this heat is not good for her nor my animals. any ideas? I thought of getting an outside person to have a look, but they would need the landlord’s permission. at this point a rotating fan is cooler than what my unit is doing. I checked, it’s not frozen up, it has a brand new filter, and it is leaking drops of water and making a hissing noise as if it’s actually working, but there is no air coming from the vents. any thoughts?

  • Samantha Asquino

    Our central air stopped working… the unit was running, but fan wasn’t spinning. Had someone come to diagnose/fix: New motor and capacitor, all seemed well… But, it worked for one day and then the same thing happened again! Called HVAC guy back, he returned and told us NEW motor was now burned out! So he re-diagnosed, and then returned with another motor and “disconnect,”hopefully to fix it once and for all. But… Now he says the motherboard is fried! It was smoking when he was working on it today. Seems to me the professional made it worse…. it was NOT smoking before we called him! Any insight as to whether this guy is incompetent, or are we just unlucky??? When he “fixed” it the first time, he never said anything about there possibly being an underlying cause. We are trying to figure out if we should let him complete the work or just cut our losses and call someone else. Thanks!

    • Don Vandervort, HomeTips

      Seems to me that, if both the motor and the capacitor needed replacement the first time, they probably fried from some kind of electrical surge, which the HVAC guy tried to solve with the “disconnect”…sound right to you? I’m not sure why the motherboard was fried after the disconnect was installed. I don’t have a good feeling for the guy’s competency. I’m concerned that he replaced the motor without diagnosing the reason the capacitor and motor fried in the first place.

      • Pat McBride

        I find that through my career, many refrigeration tech’s are not trained as competent electricians, or they would probably be electricians. So troubleshooting the root cause of burn outs require a good understanding of electrical circuits and using metering competently. Not knocking them, but it takes many years of experience and training to master both the electrical field and the refrigeration field. Ex would be that most AC companies are also plumbing companies. Electrical contractors are not prevalent in the air conditioning business. Just my two cents worth.
        Bottom line. Call another tech with hopefully more years under his belt in troubleshooting.

        • Don Vandervort, HomeTips

          Thank you, Pat. Well said. I totally agree.

  • Holly

    my air was working fine till about three days ago. I know it is getting hotter but it hasn’t got that much more in less than a week.. I called a repair man and he said it was my out side coils corroded . my unit is only three years old. how could it be that. wouldn’t my unit have been acting up before this week. it was 95 outside and it was 80 inside. The repair main said I needed a new outside unit help me its only three years old

    • Don Vandervort, HomeTips

      Sounds pretty questionable to me. The compressor should be good for many years. Check your warranty…a Trane or American Standard compressor, for example, probably has a limited 5-year warranty. Carefully read through the “Air Conditioner Doesn’t Cool Well” section above, and then read through this discussion forum…there is a ton of solid information that will help you solve this. Before replacing anything, get another opinion, but don’t tell the HVAC pro what the first guy said.

  • Pat McBride

    Don’t know the time span you are talking about. Once your AC is working, it has a very hard job to remove the moisture in the home. Could be hours. Once the moisture is gone, and the air is dry, then the AC works much faster.
    There are so many hacks out there taking advantage of folks by giving you false diagnosis just to take your money. Always call a company you trust or a company that looks professional when they reach your door. I mean uniforms, Id badges on their uniforms and a clean service truck. Not saying there aren’t some good qualified folks out there that can’t afford all that yet in their business, but just be careful when selecting anyone your going to pay out a lot of money to.

  • Tiffany Haines

    Air conditioner went out today. It won’t kick on at all. Not sure how to check fuses, but I’ve done everything else so far. Tried touching Y terminal with R and got a buzzing noise from the outside unit. Any idea why?

    • Pat McBride

      The buzzing noise was more than likely the contactor engaging in the condensing unit outside. Sounds to me like it either kicked out a circuit breaker, or blew a fuse. Check all your circuit breakers in your panel, and also check for an outside disconnect near the outside unit, and look for any fuses in it. Be careful around electricity and turn off any switch’s before pulling fuses. If in doubt, please call a repairman. Better safe than sorry

  • Randolph Heard

    The central a/c for our small house is blowing with minimal force out of the largest duct (the one that requires a filter). Air is coming out of the smaller vents. Outside compressor seems to be working. In previous summers, if one stood below the filtered duct, you were hit with a blast of cold air. Now you can barely feel the air flow. Also: the control says to Service Filter, though I have changed it a couple of times. Any ideas? Thank you.

  • D Wolter

    Central AC stopped cooling today. The fan on the condenser is blowing but the compressor isn’t working. About every 5 minutes you can hear a buzzing coming from the compressor, it lasts for a few seconds and stops buzzing. I have been hearing this buzzing noise off and on for several weeks, but the compressor would kick in and then it cooled fine. Does the capacitor also control the compressor? I had to replace the capacitor about 6 years ago because the condenser fan wasn’t turning.

    • Pat McBride

      Sounds like the capacitor that run/starts the compressor. Many of these capacitors control both the fan and the compressor. Replace it and should be ok. Make it soon or your compressor start windings will burn out.

  • Randolph Heard

    The central a/c for our small house is blowing with minimal force out of the largest duct (the one that requires a filter). Air is coming out of the smaller vents. Outside compressor seems to be working. In previous summers, if one stood below the filtered duct, you were hit with a blast of cold air. Now you can barely feel the air flow. Also: the control says to Service Filter, though I have changed it a couple of times. Any ideas? Thank you.

    • Pat McBride

      I am confused about air blowing our out of the filtered duct. There should not be any air blowing out of that. It is an air intake to the air handler, or furnace. Sounds like some kind of an air blockage to me.

  • GLong

    Colman heatpump. Outdoor unit does not run.Unit will run if contactor is manually closed replaced defroster pcb and thermostat, no help.

    • Pat McBride

      Check your condensate pump on the inside air handler. If the pump doesn’t work and gets full of condensate water, it will shut down your compressor unit. Check for the door switch on the furnace. The control transformer in the air handle, ( furnace or attic air handler). If you changed filters, maybe the door didn’t shut correctly and this will shut control power off as well. Also the contactor in the outside unit may be faulty and not picking up. Try these items. It is a 24 volt control issue. A meter would really help, but be carefull as there is high voltage in the outside unit. (240 volts)

  • Rebecca

    My AC seems to be working ok (I had it checked and the compressor replaced in the Spring), however I live in a multi-story townhouse and it is not blowing through the lower level vents, and only select vents upstairs. Wondering if this is an AC issue, or a duct work issue?

    • Pat McBride

      Replacing the compressor should not affect the flow of air. Sounds like a zoning issue. How many thermostats do you have in your home that control the air conditioner?

  • Olubode Oludotun

    I use a split air conditioner
    When I put it on through the remote
    It doesn’t come up immediately,
    The digital panel on the indoor unit flashes on and off for a couple of times
    If it manages to stay on and work, it switches off again by itself and I have to battle the remote to switch it on again
    Pls what could be wrong ?

    • Pat McBride

      Most units, or the thermostat has a 5 minute delay before turning the compressor on. This is to prevent the compressor from starting under high refrigerant pressures after running.

  • clarence123

    The system works, but no cool air. A AC repair guy wanted about $1400 to run a leak test on a old unit and fix it. I said no. Another wanted $160 to run a leak test but told me if it is in the coil you need a new one. Should I just keep contacting these AC repair guys , run the test, or get a new unit.

    • Pat McBride

      I think you live in an area that is full of rip offs. In my day, finding and fixing the leak was part of the job to replace lost refrigerant. Time and material was the cost, no a separate charge to find the leak. It sounds is if you would pay the charge for finding the leak, and another charge for fixing it, and yet another charge for recharging it. I would keep looking and pinning them down on the phone as to how they charge you. Is it a separate charge for each phase, or simply time and material for the complete repair. Where do you live that has there people that charge like this?

      • Don Vandervort, HomeTips

        Pat, I totally agree! Thanks for answering this.

  • Carolyn Mallory

    Outside fan on ac unit running but inside thermostat says filter. I looked down thru fan turning and I see snow on pipe or something…

    • Pat McBride

      You need to check and/or change the filter of the air handler. Either your furnace or attic air handler. If it’s in the attic, the filter should be in the return air grill, probably in your ceiling. The ice you are seeing is due to not moving enough air through the coils in the cooling unit. If not corrected, it will eventually damage your compressor.

  • Daniel C

    Thoughts or ideas if you dont mind.

    We live in north florida and have a Payne unit. Currently the temp is set to 74° but the temp in the house is 82°.. and the unit is not running. It runs periodically when it wants to.

    We’ve had a company come out twice already and they cant explain it or find anything wrong with the unit or indoor air handler. When its running its blowing cold air but never enough to cool the house or maintain temp. It wont return to 74° in this house until 3 hours after sunset tonight.

    We didnt have any trouble the previous 2 years and as i said nothing appears to be wrong. They did put the fan speed on high to attempt to push more airflow but it hasnt helped.

    We dont mind paying if somethings wrong but the unit is 2 years old not keeping up for no apparent reason.

    Thanks and i look forward to your reply

    • Pat McBride

      If the company you called can’t figure out what the problem is, then that company is not qualified. It sounds as if you are low on Freon, but there are many other issues that needs looked at. I always suggest to take the temp of the ambient air in the house, and the temp of the nearest discharge duct and look for a difference of 18 to 20 degrees. If it is not close to that differential, then there is an issue with either Freon charge or air moving issues. It sounds to me like it is possibly low on refrigerant and cutting off on low pressure. May other things to look at, but that will be a good start. Find yourself a good technician. Any service man that tells you they cannot figure out the problem is not qualified.

      • Don Vandervort, HomeTips

        Pat, checking the temperature difference sounds like something I need to add to the article. Thanks!

      • Daniel C

        My apologies on not getting back to you. The issue turned out to be a simple fix. We have no attic space and the closet the air handler room is in was over 100 degrees during the day. We insulated the closet from the top of the doorway and no more problems. We had just removed 30 large pine trees from the yard during the spring and it looks like they gave us more shade than we thought…. however it wasn’t the technician that solved the issue. It was my girlfriends dad who ultimately figured it out. Thank you :)

  • Jennifer Bauer

    Our ac fan was not spinning so we had capacitor professionally replaced. Even though air is cold coming out of vents, there is almost no air flow at all, as if set on low and prior to this was set on high.
    We have changed the filter, cleaned the coils, reset the system a few times, and looked for a low with high switch on the a/c unit, there is not one. What else can be causing almost no air flow out of the ducts? When it is set to only the fan setting, there is strong air flow, but when set to cool and the outdoor unit kicks on, there is about 20% air flow. It was not like this prior to yesterday when the capacitor failed.

    • Pat McBride

      Perhaps he put the wrong fan motor in. There are different speeds and it may not be set to the high speed needed for air conditioning. You furnace will run on a lower speed in the winter as hot air is easier to move than the heavier cold air. Have your technetium check this. Although he should have checked it to begin with. Take the ambient air temp in your home and take the air temp coming out of the closet vent to your ac. There should be between and 18 to 20 degree diff. No more and no less, within reason. Too clold means your blower is not moving enough air. Any warmer means that there is too much air across the blower. There could be other issues involved, but this is the first thing to check.

  • 1aspiemom

    My ac is not cooling enough. We assumed it was because the inside unit was dirty because we could see dust on it. Repairman sprayed with coil cleaner and brushed dust off. Still didn’t cool well. He came back and checked freon and pressures. Pressure was off, so he thought it was the compressor. Changed compressor and dryer, filled with freon. No improvement. Will keep up at night, but not during the day. Pressure still shows to be off.

    • Pat McBride

      You need another service tech. This man evidently doesn’t know what he’s doing. I have seen, over my years in the business, so many compressors replace by misdiagnoses. They will never admit it. Don’t ever have a compressor replace without a second opinion. This man ripped you off due to his lack of ability to trouble shoot, at your expense. Get another tech. period.

    • Pat McBride

      Any technician that tells you your compressor needs to be replaced should also be able to tell you exactly what cause that compressor to fail. Especially if it is less than 10 or 15 years old. I have never replaced a compressor unless I knew what caused it’s failure. There will always be a root cause that will simply take the new compressor out sooner or later. This is called being an experienced and well trained technician. If he can’t, then call another tech. My advice to keep you from getting ripped by an unprofessional tech. Compressor replacement is not cheap so make sure you can depend on your tech. With this heat wave, the fly by nights are crawling out of the woods.

  • Steven Shaw

    My central air is doing everything except blow out cool air what is most common problem?

  • Victor Cepero

    Just clean the coils. I turned my unit off at the outside box now it will not turn back on has anyone else had this problem?

  • Jen Sims

    Island Air Conditioning Split unit it is it was built in 98 and still runs it’s nice and cold but not freezing but it’s cold it runs but it’s leaking water everywhere water is being blown from the blower on to the floor and not into the drip pan I’m not sure what to do if it’s been thoroughly cleaned it’s been maintenance by a guy then they told me it needs Freon which is $700 to just do that on top of the thousand dollar maintenance they did to it did not fix the problem which it didn’t fix the problem cuz it’s still dripping all over my floor it still drives it still works everything works but it just drips onto the floor I don’t know what the problem is another guy told me I need to replace the system I’m not sure what to do any suggestions would be appreciated

    • Pat McBride

      If it’s cooling, and not forming ice on the lines, then it should not need Freon. Take the temp of the amibient temp of the room and the temp of the air closest to the AC discharge air. It should be 18 to 20 degree difference. That will tell you if the AC is working right and the problem is in the waer removal. I would get another opinion. the water channels in the cooling coil section is not clean. it will make a lot of water on hot humid days and the water channels in the evaporator, *the cooling coils) is directed either to a drain or a pump that takes the water to a drain. The prices you quoted, to me, is extremely high, but that may be the going rate in your area. For the money you are talking, I would get another tech from a reliable company for their opinion.

    • Don Vandervort, HomeTips

      Jen, please see the info in our article about the condensate pump. It sounds like none of the condensation is being properly collected and pumped out. I agree with Pat, below, about talking to a different AC pro.

  • Karen Kay Ogden

    My brother is,saying the compressor is cutting off before the house reaches correct temperature???

  • Elena

    After working just fine, suddenly Ac unit oitside goes on fine but after about an hour shuts down. Initially noticed outside unit running but fan not turning. After a day of non use unit started fine but now shuts off. Any suggestions please?!

  • Kelly

    We purchased our home last November so this is the first summer we have used the AC. When we first turn it on, it blows cold air. After about an hour, the air is warm. The house temp will go from 72 to 74. When I turn off the unit the temp will drop to 73. We will wait about an 1/2 hour and turn it back on and it is cold again for a short time. I have had a technician come out and he has topped off the freon, checked for leaks and says it should be fine. We had a friend suggest we check the damper to see if it was open (they had a similar problem and this fixed theirs). We could not find a damper on our unit. Any suggestions?

  • Brian Wilkie

    I have a 2009 Trane XL16i – outside fan is running, air handler is running, air being blown in the house is warm. Compressor is NOT running, but the fan is…is it still possible that the start/run capacitor is bad if only the compressor is not running but the fan is?

    • Pat McBride

      Read the above troubleshooting guide. Don covers that topic real well. Be careful working with high voltage on the contactor. Turn the power off and check the contactor for welded contacts. This is a common problem.

  • ColleenSiegel

    Hi This is my 1st summer owning this house. My electric bill has been doubling for 3 months in a row..I have a Carrier 25HPA6 Performance Series 2 Stage Heat Pump…I recently went online and found instructions on how to clean the outdoor unit. I did so and it was not very dirty. I also have a generator that kicks on when I lose power which does not support the AC unit..We did lose power for a few days recently. I have 2 faults showing on the heat pump being 53 outdoor air sensor not reading or out of range 255 events and F 37 control fault, heater stuck on 13 events. I have never had a heat pump or central Air and am very green to this. PLease help?

    • Pat McBride

      You need to find a good tech. It may be the your electric heating strips are coming on due to that defective sensor. It may think it needs emergency heat and maybe even trying to defrost. A service call may be less expensive than the electric bills.

      • ColleenSiegel

        OMG! Had a service tech come out yesterday and bingo the heating strips are stuck on and the tech is going to check on the cost of a relay switch and get me an estimate..Was well worth the $89.00 diagnostic fee. Any idea the cost to fix something like this. Thank you for your insight Pat McBride! I appreciate it. Last month the electric bill was $330!!!

      • ColleenSiegel

        Is a sensor the same as a relay switch? That is what my tech thought was the problem causing the heat tape to be stuck on. Is it a costly repair? You are genius. Thank you very much. BTW my electric bill jumped to a whopping $330 last month which surely caught my attention.

      • ColleenSiegel

        Am I supposed unplug the heat tape when no longer needed for the season? Is there anything to do to the ac before winter?

  • Dan

    Hi. Downstairs AC blowing cool, but not cold and less pressure than usual. Fan outside is spinning fine, but the air coming out of the outside unit is cool, while the air coming out of the unit for the upstairs AC is warm (which is what I think is supposed to happen). Why would the air coming out of the outside unit be cool? Does that give any clues as to why the AC downstairs isn’t cooling as well as it should be?

  • carol doss

    My central air is not working right, we have it set on 72 and in the early morning it blows out cold air but after it gets warmer outside, it doesn’t blow out cold enough air, it comes 79-80 degrees in the house, had it checked, said it had enough freon

    • Pat McBride

      Take a real close look at the condenser coils on the outside unit. Probably dirty making it inefficient during the hotter parts of the day and will work better at night when it’s cooler outside. Check them very closely as with fine fins, they can be hard to see through. Use a flashlight if you have to. You want to see through them very clearly all the way up and down the colils

      • Don Vandervort, HomeTips

        Pat, once again…thank you very much with helping answer these questions…your answers are great!

        • Pat McBride

          Thanks Don. I miss the business of trouble shooting machinery. I was also an Industrial electrician for about 40 years working with machine automation and PLC controls and supervised foundry maintenance departments for 20 of those years. Just let me know if I step on your toes in any way. Just having some fun here. .

          • Jennifer Barnes

            Hello, my central air unit runs, but is only blowing out room temperature air. It won’t get cooler than 84-85 degrees in the house. It was working fine before then. Any suggestions? Thanks!

  • mike

    My air conditioner is not cooling. The heat does work. I turned it off for a week while on vacation. It was working before I left and would not work when I got back. I have been told that it has plenty of charge…the guy said it was the compressor…I’m not so sure. I have replaced the thermostat, start capacitor and hard start kit. I have power on all 3 legs of the compressor. Ohming the compressor leads are: C to S = 1.5 ohms, C to R = 4.25 ohms and R to S = 5.5 ohms. All three leads are open to compressor case. I let it run all night. In the morning, top of compressor was slightly warm, but easily touched. All 4 lines coming off of the reversing valve were slightly cool to touch. Any thoughts?

    • Pat McBride

      Call someone else. How can the man say the charge is correct and in the same breath say he it could be the compressor. That’s silly. A heat pump is very complicated to trouble shoot electrically concerning the controls, not the pump necessarily but there are lot of things that can go wrong with the controls If I was to guess, I would point at the reversing valve that changes it from heat to cool and defrost. Those are common to fail. Call a heat pump tech. By the way, those are good ohm readings Any bad readings and the pump will not run. If there is an issue with the compressor (pump) it would more than likely be in the valves and they are easily tested on a heat pump.

  • Jennifer B

    I just moved into a new townhouse apartment last week. I live near the beach in southeastern VA and it’s been in high temps here so while my dad was helping me move, he turned the thermostat to “on” and to 65 since it had not be on for a few days and was really hot both inside and outside. The next day I noticed a leak in the ceiling in the downstairs bathroom. I reported it to maintenance and when I returned home there was note saying I had the temp too low and needed to set it to “auto. i completely forgot to change it back with everything going so I immediately set it to “auto” and 68 (my norm). 2 days later and I get another note from the maintenance guy saying I need to keep my AC on auto and set between 73-75. Yeah right, it is at least 5-6 degrees hotter upstairs. So much so that I can hardly sleep and that’s if the temp is on 70. I have to dry and style my hair downstairs in the living room due to the high temp and humidity upstairs. I was raised in a cold house and I cannot sleep in a hot room even with my trusted powerful box fan on high blowing right on me. Yesterday I turned the AC completely off for a good 12 hours while I was gone and the ceiling is still leaking. And, you can tell they’ve fixed it before by looking at it. It’s gotten worse actually. i now have my temp set to 68 so I can sleep somewhat comfortably soon and it’s steady leaking. What is causing this? I’ve always lived in older apartments on the top floor and never had this issue before. I’m used to paying high electric bills due to the heat rising and having to combat it. If I had known there was an AC problem or temp issue before I signed my lease, I never would have. This all makes me so sad. Please help me!

    • Pat McBride

      Your ac will condensate more at higher temperatures than lower as it removes the humidity as it cools, so the cooler the air, the less humidity. Your maintenance people are not looking at the real problem If the moisture is coming from your ac, it’s either because the air handler is above the leaking ceiling and the condensate drain in not working, or the duct work leading to the upstairs is not insulated. Or there is a plumbing leak. If you are tied to a long lease, you may want to hire a contractor to determine what the issue is and pass it on to your apt manager, and ask to be reimbursed. You may have a contract that forbids this, so check out the legalities. But the maintenance folks are on the wrong path IMO

    • Don Vandervort, HomeTips

      Jennifer, it sounds to me like the AC unit is producing a lot of condensation, especially when set to lower temperatures because it runs most of the time when set that low. That condensation needs to be pumped out of there with a good condensate pump (or the drain lines need to be cleared).

  • Rob Johnson

    My AC works fine overnight and during the morning, but by late afternoon and evening it comes on from time to time, but not enough to get down to the 77 I have it set for. By the time I go to bed it is up to 83 or so, but overnight it starts working fine and by the time I get up it is 77 again (we live in Florida and outside temp is still in the 80s overnight). Had the AC checked and they say everything is fine, but for at least 3 weeks, it doesn’t work right and the evenings get warm. Any ideas? I live in a small, 1,000 sq ft condo, with my own compressor and air handler.

    • Pat McBride

      Check your condensing unit. I think it is dirty and not moving enough air to cool it. Look at both the inside an outside of the coils. Take a flashlight and hold in on one side while you look through from the other side. I feel I am safe in saying your condenser coil it plugged. It’s cooler at night so the unit will work a bit better. Let me know if that is the problem please.

      • Mak Koon Liang

        Check or replace the fan capacitor. If the capacitor is faulty or below capacity, the fan doesn’t turn fast enough to cool the hot condenser coil.

        • Pat McBride

          I believe that if the fan capacitor is bad, the fan motor would not run, cycle on and off, or burn out after a while. Another possibility would be a low refrigerant charge. Enough to cool when the load is lighter, but not enough to cool during the heat If it;s a thermostatic controlled refrigerant valve, then it has an accumulator to store excess refrigerant and release it when the demand is higher.
          There are several possibilities. Would be nice if Rob were to let us know what was found. Just curious

  • Brian G. Ainsworth

    My fan out side spins when you turn it on but then stops hums and the motor gets really hot. It this the compasitor?

    • Pat McBride

      Yes. I do believe it is the capacitor. It may be a duel capacitor that also starts the compressor. Make sure you get an exact replacement and safely turn off power before attempting any repairs. Also test to make sure the power is off. You may want to call a tech for this unless you feel safe in taking this on. Maybe you have an electrician friend.

  • Anna

    My ac fan kicks in and spins for about 30 seconds but does not flow air into the house then fan shuts off. It Keeps trying to come on every few minutes but does same thing repeatedly. Please help!:/

    • Pat McBride

      It could be the motor run capacitor, or just a failing motor. You need to check the filters, although I don’t believe that would necessarily be the problem, but check the filters anyway, then call a dependable HVAC company or an electrician friend to check the run capacitor for the fan.

  • Dorothy

    Had a storm come through last night didn’t seem bad at all but the electric went off and came back on 4 times rather quickly. After the 3rd time I shut off most everything in the house, including the central air. After about 30 min of the power staying on I turned the air back on. It kicked on and seemed fine. A few hours later when I was headed to bed I took notice to it being rather warm in the house. There was a 4 degree difference in the room vs the thermostat setting. Went down to check the unit, looks like it was starting to freeze up. Pulled the one filter out and it was wet. Came back up shut it off and have been wondering what to do, if there is an easy fix I could try before I call someone.
    I read somewhere online to turn it on but just the fan not the actual a/c. Is that all it might need or do you think the power going off and on quickly fried something?

  • Dawson

    Would love to get your opinion on my recent Ac issue.

    Just purchased a new home last winter which had a brand new ac cooling unit installed, it has worked great all summer up until I woke up this more, hearing a weird buzzing/clunking sound, I check the thermostat it was set a 73 but room temp was 75, the furnace blower motor was not running so I went out back and the sound was coming from the cooling unit. So I turn off the whole system waited for a few minutes, turn it back on and same results. I notice lots of condensation coming off the cooling lines like I have never seen before, it’s like the condenser is running but nothing else. I am now just running the furnace fan by itself just in case the system froze up.

    Any other thoughts for trouble shooting?

  • Linn Burke

    The fan on my central air unit outside quit working. I did spin it by hand. It did take off just not as fast as before and got very hot. What do you think my problem is?

    • Pat McBride

      Have an AC tech check the fan run/start capacitor. Please let us know what was found to be the problem.

  • Bill Kurple

    outdoor unit fan is running but the compressor is not running. It is not buzzing or making any sound. The contactor is working. I had the coil replaced in the winter- is it possible the winter repair had a leak and I lost the refrigerant?

    • Pat McBride

      The contactor also runs the condenser fan. Replacing the coil would not affect the refrigerant charge either. It is possible to have a leak aside from the repairs. It’s also possible that the compressor motor has burned out. You need an electrician fan to ohm the motor and trace the power to see where you loose it. Best off to call a good AC tech to also check the R charge. Good luck and let us know what was found please.

  • Gerry Nance

    I have one unit, two thermostats, air is working but does not maintain the desired temperature. The upstairs intake is sucking well, the downstairs intake is not. I feel now air coming out of vents. AC Guy was here last week and replaced a pressure valve on the outside unit. This problem seems to be going on since then. Could it be related?

  • andrem

    Outside AC unit relay keeps making a clicking sound and the AC is not blowing cool.

  • Michael Gouker

    I scanned the q&a here and didn’t really see exactly my problem, so here are the details:

    1. The AC mostly works. Good, right?
    2. Sometimes (always in the evening) it turns off, but not at exactly the same time. 7 pm to 9 pm, sometimes not at all.
    3. When it turns off, the condensate trap pan is dry (so it doesn’t appear to be the automatic flood off switch.) When it is running there is a steady normal drip down the condensate drain outside. I have two air conditioners in the house, and the outflows appear the same.
    4. If I wait a while, I can turn the AC back on and it works.
    5. I checked the schedule of the unit and the cool temperature (we keep it cooled to 78 F) is the same.
    6. The refrigerant line is cool to the touch, identical with the unit that is working fine.

    Any help would be appreciated. I’ll look for more clues tomorrow.

    • Pat McBride

      I’m not understanding what your complaint is. Does it cool ok when it runs?

      • Michael Gouker

        Thanks for your reply, Pat.

        My complaint is that it’s not supposed to turn off. ;-) We washed the outside unit, made it perfectly clean, drained out the pipes again, and tested the refrigerant levels (they were ok). So far, it’s still working.

  • bobp

    central outdoor air cond. has power to the unit but will not start. no sound at all coming from unit. bought new thermostat still nothing. checked for loose wires.

  • Marian L Fischer

    We just had a brand new carrier unit inside and outside put in 1 week ago, we have it set To 75. It gets to the 75 overnight, but as soon as the sun comes up my thermometers In different parts of the house rises to 78. It stays at 78 all day . I’m sure sometime after midnight it gets to the 75. Why doesn’t it maintain the 75 all day? I’m afraid to cook and heat things up.

    • Pat McBride

      You need to get back with the installer, sales company. It may be possible that it’s undersized. When the temp starts to rise, check temp in the home, and the temp coming out of the nearest discharge register to the furnace. Should be approx. an 18 to 20 degree diff. Let us know.

      • Don Vandervort, HomeTips

        Pat, thanks so much for helping out with all of your expert answers!!

        • Pat McBride

          Thanks Don. I miss the trade and enjoy the challenge. It would be nice if folks responded more to let us know it we’re on the right track. It sharpens our skills as well. Not always right ya know. Imagine that.

          • Don Vandervort, HomeTips

            Hey People, you have a real expert here in Pat. When he helps you fix your AC issues (or if his answers don’t quite work), please jump back onto the site and let us know!

      • Marian L Fischer

        Thank you. We Did call the installer they sent a different technician out. Their was a wire either loose or not hooked up properly. Now we can actually hear the unit running in the house where before it was so quiet you couldn’t tell it was on. I knew something was wrong. Thank you.

    • Don Vandervort, HomeTips

      This one is hard to diagnose from this information. Different rooms will read different temps, depending upon exposure to the sun, etc. Make sure your AC’s thermostat is set properly. Sorry I can’t be more helpful.

  • Shane M Lafty

    I have a black n blue wire not connected were does these wires go

    • Pat McBride

      Not enough info. Where are these wires located? Are they small solid wires? Some thermostat wire cables have more wires in the cable than is needed, Have they been stripped back to show the copper? You have to be more descriptive. Does the unit work? Get back with us.

  • Margaret Headrick

    When my central unit reaches desired temp. the unit keeps running and blows warm air, and does not go to off position.

    • Pat McBride

      Check to see if the fan setting on the thermostat is set to on, or auto. On runs the fan continually, auto runs the fan when the AC, or furnace is calling for heat or AC.

  • StereoGuy

    Hello, I hope you can help me. My problem is becoming more frequent. My unit works fine for a few days and then all of a sudden I notice that the house is getting warm. The outside unit (compressor) is running but the inside unit is not. The lines and coil freeze up solid. I turn off the breaker, let it melt and turn the breaker back on, and all is good for a few more days. This started a while ago and was originally happening only every other month or so but has gotten worse. I should note that I have caught it a few times before it was all frozen and a breaker on & off fixes it every time. My unit is a 7 year old Trane with a variable speed fan motor. I have also started hearing a hum from a transformer on the inside unit. Thanks in advance for your help.

    • Pat McBride

      That transformer hum your hearing may be a fan relay. Depending on the type of unit, there is normally no transformer in the air handler. You say you noticed the outside unit, (condenser) is running, but the inside fan is not, and you have a variable speed fan. This is where I would suspect the problem to be. The variable speed controller may be causing the motor to run too slow causing the gradual ice build up. Resetting the breaker may be resetting this controller. You can bypass this controller and have you fan run full speed continually. This will isolate the problem. Make sure the return line is flashing cold and sweating when it’s running to show that the refrigerant charge is adequate. This can also be determined by taking temps of the discharge air from the register closest to the air handler. There should be a 18 to 20 degree difference. It may be a bit low on charge and cause the icing up as well over a period of time. I would appreciate letting us know if any of this makes sense or corrects the problem.

      • StereoGuy

        I think I figured it out. The fan inside was not running at all (not even at low speed) and it would ice up quick. Turning off the breaker gave it time to defrost and also reset something. It would work fine for a few cycles and then……same problem. I replaced the contactor in the inside unit and everything seams to be working now (2 days and all good). Ever since I replaced the contactor, the transformer has stopped humming. And yes, my unit has a transformer inside the inside unit. If it fails again, I’ll let you know.

        • Pat McBride

          curious how it ran for days before noticing it wasn’t cooling. Without the fan running, it would ice up and stop cooling fairly fast. Glad you found the problem and are staying cool.

          • StereoGuy

            Maybe I miss-spoke. It would cycle on-off for days just fine and then all of a sudden on one cycle the inside unit wouldn’t turn on and would freeze up quick……also, not sure it’s fixed now. The problem has recurred once since then. It may have something to do with the float switch. It “seamed” that the float switch (when tripped) is only preventing the inside unit from coming on but it’s letting the outside unit continue to run.

      • StereoGuy

        I wanted to follow up on this as I finally fixed it. After not being able to reset the unit, I called an A/C guy to look at it (and watched over his shoulder). I noticed that he found that the harness that went to the fan motor (18 pin) one of the wires had corroded out. When he pushed it back into it’s hole the fan kicked on. He then told me that the fan was going bad and it was $1,700 for a new variable speed fan. I told him “forget it” and just paid for the service call. I ordered a new harness online and that “seamed” to fix the problem for a while. However after about a month, the problem started recurring and I was waking up to a warm house….and a frozen air conditioner. My next guess however fixed it permanently. I ordered a new Fan Control Board and it hasn’t failed since. All in all, I replaced a harness, contactor, transformer and fan control board all for about $150 and it’s fixed. Much better that the $1,700 that I was quoted for a fan that I didn’t even need. I wonder if that new fan would have come with a new harness and board???

  • Pikkauhn

    Hello, I am just about at my wit’s end with this issue… I do not have 24 volts getting to the contactor, however when I manually press in the relay for the contactor, the unit appears to operate normally (fan and compressor kick on), but the air handler still only blows out hot air. Last summer the air handler motor had a broken mount and we replaced the motor ourselves, as well as the air handler. We took pictures of all of the wiring before disconnecting anything and are certain it is connected back properly, as it was working until this summer. I have also replaced the contactor, changing one wire at a time to ensure that each wire is connected exactly the same. Replacing the contactor may not have been necessary, but some of the contacts on it did look slightly pitted. I have noticed that the wires coming from the thermostat/air handler into the outside unit connect into a defrost board before connecting to the contactor, could there be an issue with the defrost board/circuitry?

    • Pat McBride

      There is a float in the air handler, or the condensate pump that will prevent the outside unit from running if it doesn’t drain the water correctly. Is it possible that this got moved or damaged when replacing the fam motor? The 24 volts goes through a number of safety’s depending on the brand and the age of the unit. Follow the wires out until you find the device that has it shut down. Also, give it at least 5 minutes after the thermostat calls for cooling. When the thermostat is satisfied on temp, most units has a 5 minute timer to prevent short cycling of the compressor.

  • Steve Pojda

    I was checking my unit out while my heater was on .Curiosity made me put my hand on ac compressor was getting cold .is this normal.Forgot to say my ac not blowing.That’s the weird thing heater works fine .I’ve concluded control board bad have nice little brown spot .Hoping I don’t have 1more issue and I hope I’m making sense.One more thing what brought this whole thinup I replaced my thermostat in Jan of this yr.2017 turned it on heat worked fine didn’t turn ac on until last wk. What the hell! ac worked summer before .

  • Nnschiz

    Help! My AC isn’t working. When I turned it on this morning, air started blowing out of the ducts inside right away. After about 30 minutes I realized that air was still blowing out of the ducts but my house was only 1 degree cooler (based on what the thermostat read) and you could feel that the house was not cooling off. I went outside to check the unit and it wasn’t on (but air was still blowing out the vents inside) while I was outside it kicked on (fan spinning and all) for about 15 seconds or so and then went off. I have since turned the whole unit off because I don’t want to burn anything up. Does anyone know what is going on with my unit!?

    • Pat McBride

      Could be dirty condensing unit shutting down on high pressure due to lack of air flow. It could be that it’s low on refrigerant and shutting down on low pressure. There are other possibilities also, like a compressor failing and shutting down on high amps. It could also be a defective run capacitor on the compressor as well. You need to have a tech check it out as it probably calls for metering to diagnose.

  • Michael Graf

    I need some help on this one. My a.c. runs fine. The air is cold and the house seems to get cooler. However if the thermostat is set at 73 the a.c. will run and continue to run even when the thermostat says that is 72 inside. If I go and manually change it the temp aetting to say 74 the ac shuts off. It will then turn back on when the temp reaches above 74. The problem isnt the ac turning on it’s that it doesn’t automatically turn off

    • StereoGuy

      sounds like a bad thermostat

    • Pat McBride

      Digital thermostat or mercury? Could be out of level if it’s a mercury, or the heat anticipator set wrong. Is the thermostat in the sun? Is it on an outside wall? How old it the unit/thermostat. Many questions mostly pointing at the thermostat.

  • Teckla Thompson

    Help.. My AC won’t kick on. The breaker in electrical panel is tripped and won’t reset. Could it be bad fuses outdoor ib box near unit? Or a bad breaker?

    • StereoGuy

      last time I had a breaker that wouldn’t reset it was the compressor that shorted out. I’m not an A/C guy but that’s my experience.

      • Pat McBride

        Could be the fan motor, but you are more than likely correct. Regardless, it need an electrician to check it out, or a good refrigeration/AC tech High voltage can hurt, or kill. Be careful. And remember, capacitors can hold a charge for some time.

  • Alex Wells

    Ok so I have a trane xl16i outdoor unit that quit working the other day. So me being the diyer that I am decided to take a look and I found 2 fried snakes around the capacitor. I changed the capacitor yesterday and when I flip the breaker the unit will run for about 4 hours drop the temp a few degrees in the house then die. Any ideas or advice would be awesome thanks

  • Jasmin

    Our AC blows air but it’s not cooling inside and the fan is not spinning and making some noise. What would be the cause/problem of it?

  • Michelle

    My a/c works, but we have to reset it each time for it to work. The heat works fine, but if we switch it from heat to a/c, the a/c won’t cool unless we turn off all the breakers, wait 20 minutes and then turn them all back on. Any ideas what the problem could be?

  • Stephanie Davis Kindle

    AC doesn’t come on inside but fan blowing outside. Right before this the smoke detectors alarmed and there was a burning smell in the house. No source could be found. Next we discovered AC not working.

  • Kris Snopek

    exterior AC unit wont turn off. Last year, all was running fine. We recently turned on the ac for the first time this season. (yes we replaced filters & such) It was running fine as far as we knew. Then the weather got cooler so we turned off the AC at the thermostat that evening & went to bed (no heat/no AC on at all). When I went out back the next morning to the garden, I found the outdoor unit was still running & had ice on the pipes connecting to the unit, despite the thermostat being turned off. I shut off all breakers & let the unit thaw. My first thought was the thermostat went. So I replaced the thermostat but every time I wire it, the outside compressor clicks on & begins to run even thought the thermostat is set to off. The only way to shut it off is to un-wire the thermostat or turn off the breaker to the outside unit. Concerned it might be a short in the wire to the thermostat, I rewired the thermostat & I tested the heat. This seems to be working fine with no issues at all & clicks on with no problem & shuts down with no problem when it comes to temp. So, correct me if I’m wrong, but I figure if the heat is working fine that there is no short in the wire to the thermostat & that the issue must be with the outside unit in some way. ANY SUGGESTIONS???? Thanks in advance for any suggestions or advice that might be provided

    • Steven B

      Try checking your contactor and make sure it is not stuck. Your thermostat will send a signal to your contactor to open or close depending on the temperature set point. This contactor when closed engages your compressor. Disengaged when open. Turn your condenser off at the breaker before checking. You will find directions online if you Google your make and model A/C

  • Tomi

    Ac blowing but not cooling, had someone come check it and they recommend it to replace the unit which is very pricey. What are my options to fix it and if I really need to replace it, how much should I be paying?

    • Pat McBride

      Get another opinion from a reputable HVAC company. Some companies are simply salesmen, If he can’t tell you exactly why he recommends replacement, and what exactly is wrong with yours, then you can’t make an informed decision. How old is this unit?

  • Marian L Fischer

    We just got a new carrier, huge one, $7400 worth. We had it set on 76 and it stayed at 78 inthe house. So I fought to get the installer back, turns out there was a wire loose. Now we can tell it’s running, but rooms were still hitting 77-78° during the day. Turned it down to 74, the only room nicely cool is the living room, bedrooms at that end of house, mine stays at 77-78. What does That ambient degree or temp mean? My kitchen stays at 77°, 78-79 if cooking! I want to call another separate a/c company to get a review of the work done. Sounds reasonable? Thanks

    • Don Vandervort, HomeTips

      With a typical system, different rooms are going to have varied levels of cooling. Size of ductwork, distance from the A/C to the room, and the solar gain (south or west side vs. north or east side) are all going to make a difference. You probably need to have somebody come out and try to balance the system. The other option is to go with a zoned system (see

      • Marian L Fischer

        Thank you, that sounds reasonable . I will call the installer back out here. It’s funny though, if we turn down to 73°. It goes to 76 at least throughout the house. Thanks again

  • Gerda Richmond

    My Carrier A/C runs but not steadily. It comes on then goes off a second later and it does this all the time now. It is about five years old. The unit sits on the roof. Please give me your best guess. Do I already need a new one? Thank you.

    • Pat McBride

      That is an indication that it is low on refrigerant. But could be other things, like a plugged condenser not allowing cool air to flow and it’s over heating. Could be a dirty filter causing low pressure to cut out. You need a tech.

  • Joe

    Have an older central air unit needs to be recharged every summer. Called a service guy to rechargce, said yes there’s a leak but the only way to see if it will hold freon is to give it a full charge that it won’t work properly if it doesn’t have proper amount of freon. Is this correct? The next day freon had leaked out $190 wasted. He said they don’t really fix leaks because there could be several and too expensive to fix. Is this correct? Thanks, joe. Chicago

    • Pat McBride

      Absolutely not correct. They are not a service company if they don’t locate leaks. In fact, if they are charging this unit annually or more. There is a law that requires service companies to repair leaks if over a certain amount of Freon is expelled into the air. I don’t remember what that number is.
      But the point is, you need a reliable service company to find that leak and fix it.
      Also, the excess Freon is what cools the compressor motor. Every time it runs low on refrigerant, that motor is getting extremely overheated. Get another tech in there before you loose the compressor. These people are only Freon salesmen. That’s all they know how to do IMO.

      • Joe

        I agree with you this is the first time I used this company. The unit is about 29years old and he was assuming there would be more than one leak and between repairing and more Freon that was already wasted the cost would outweigh fixing the old unit. Said a replacement would run about 2,750. I have tenants renting so for this year I had to go out and buy some window units to get them through this summer, Hopefully will be in a better situation next year to fix it/replace it, Thanks for your response.

  • Patty

    My AC unit stopped cooling my home. The fan is running outside and I do hear an occasional “hum” coming from the unit. I was told that the compressor was bad and that I needed to replace the whole unit. What’s weird is that it was working just fine the day before. I am disabled and on a very fixed income and unable to afford a new unit. I have difficulty breathing when it is hot and humid and desperately need my AC fixed. Is there any advice you can offer??

    • Pat McBride

      A service tech needs to check the capacitor for the compressor. You didn’t say if any one tested it and confirmed that the compressor is bad. If it was diagnosed over the phone, then call a dependable company that is not just out to sell you a new unit. If it was looked at, did the tech take a meter and check the compressor?
      Tell them what you told us. You can’t afford a new unit so you need this one fixed if it’s a reasonable price.

      • Don Vandervort, HomeTips

        Pat, thanks so much for all the help you have given to the discussions in this forum!!

  • Scott Bellamy

    I live in an apartment and my AC does not cool my apartment at all during the day. If it is 90 outside my AC temp gets up to about 86 and keeps running. I have my AC set on 78. Shouldn’t the AC keep your apartment at the temp you set it at? I know that each room is going to be different temp’s. The people at my apartment complex say’s the AC is not going to cool my apartment to that temp and keep it there.

  • Joe

    Last year my central air stopped working and I found the capacitor “exploded” apart. The top was off when I looked into. I replaced it with a capacitor from grainger. I made sure all the numbers matched. The only difference was the maker of the capacitor and it was a lot bigger in size than the old one. It worked “ok”, but it was not cooling like it used too. It was towards the end of the hot season so I waited until this spring to have it tuned up and checked by a pro. It worked fine at that time. 10 days ago it stopped getting to the set temperature again. I noticed the copper line outside freezing over. I had a pro here 5 days ago and he couldn’t get it. The next day a “master” pro came and thought he found the problem. Well, the lines aren’t freezing anymore, but it is still not cooling. I am going to call them back because they have a 90 day guarantee, but I am looking for anything I or they might be overlooking. It seems like an air flow issue, so I will be vacuuming out the ducts today. Thanks for any help.

  • Debbie Dixon

    Hi, I’ve searched everywhere for an answer to what’s going on with my A/C, so hoping someone can help. The heat worked fine all winter, then when we got the first warm day here in Michigan, I set it to cool, and tried to set the thermostat, but I didn’t hear the “click”, and it never came on. I decided to take the cover off of the thermostat to check the wires, and as soon as I took the cover off, it came on. It seems to be cooling okay, though we have not had really hot days. It will not shut off, unless I put the cover back on… I am clueless as to what is going on, and really don’t want to call a service person, until I do have at least some idea of what could be going on. I bought a new thermostat, (replacing it with a digital thermostat), thinking that was the problem, but when I tried setting it up with the same wiring as the old one, it just runs constantly, with no way to shut it off, so I put the old one back on, just so we can have some air until I can afford a service call. Any thoughts? Thanks!

    • Don Vandervort, HomeTips

      Hi Debbie,
      Wow, this sounds frustrating. You tried what I would try first—replacing the thermostat. But you say you set it up with the same wiring as the old one. Be sure to read the instructions for wiring the new one rather than just replacing the wires per their colors, etc. The new thermostat might have a slightly different wiring configuration. Sounds to me like it’s mis-wired. Please let us know what you learn.
      Please see the discussion below from 2 months ago between Kris Snopek and Steven B.—looks like the same issue. Steven say’s a “stuck contactor” may be the issue.

      • Debbie Dixon

        Hi Don, as it turns out it wasn’t that the thermostat was bad. I have an older mobile home with a cool/heat switch on the furnace itself. The thermostat must stay on heat, at all times with this unit, in order for it to complete the circuit. You change the heating or cooling with the switch that’s on the unit itself, which I did, I just wasn’t aware of the thermostat (having to stay on heat). I haven’t had the home in the summer, until now, so I had no idea.

  • John Redman

    I’ve got a 18 year old 3-ton Rheem outside central air unit. The repairman came out and recharged the unit which was totally out of Refrigerant. He said it had a leak on the low pressure side. Whatever that means…Then after charging me $198 he said the necessary repair to the unit would be $3175. or $4346 for a new Seer. SInce I can’t afford either, being on a fixed low income and retired with no credit rating, is there a reasonable way to get this fixed?

    • Don Vandervort, HomeTips

      Some types of leaks can be repaired…but that seems like a lot of $$ for repair. If he tested for the leak and found it (rather than just checking the pressure), ask him specifically where it is. Then get bids (and opinions) from a couple of more AC contractors. Be aware that they would rather sell you a new unit than repair the old one because a commission might be involved.

      Also, see the discussion between Joe and Pat McBride a month ago (below). It involves a similar situation.

  • Jo Buckmeier

    Help! Our ac is running but not keeping house cool. Had ac guy come out, unit freezing up. Turned off unit and acid flushed lines, worked one day. Tech came out again and changed motor and fan. Unit started to cool off house after about six hours. It was at 72° at about 8 am, it is now 79° in house at 1 pm. What else could it be? Evaporator coils, capacitor? We can’t afford a new unit but also can’t live with it being 90° in house. Thanks everyone!!

    • Don Vandervort, HomeTips

      As far as I know, two things cause an AC air handler to freeze up. By far the most common is reduced air flow because of dirty filters, coils, or poorly working fans (which, it seems, is what your tech figured). The other is low refrigerant level, which a pro must check and, if necessary, recharge. If I had paid for a day’s work and a new motor and fan, I would want the tech to tell me why he did these things and yet I still don’t have satisfaction. Then I would expect him to come out and give me a great deal on getting it right.

      • Jo Buckmeier

        Well after trying everything, we had to replace the whole unit. So now we have a brand new ac unit, for a day or so it stayed cool but now by 11am or so it’s about 80 to 85 in the house, temp is set at 72. I have asked and they have checked all vents saying no blockage. Thinking they put to small of a unit on the house, it’s a lot smaller than my old one but im still having to run fans and keep all blinds closed. What do you think. I think I should call them out on it. Help please jo

  • John Redman

    Can a leak on the low pressure side be repaired reasonably?

    • Don Vandervort, HomeTips

      John, hopefully an AC contractor who visits our site will answer this. Please see my answer to your first question, below.

  • Zzyzx

    Hi there. I have a condo-sized central A/C situated in the hallway ceiling. It’s about 10yrs old. My thermostat is there also. After being out of town for a few weeks, I returned to see that batteries in the thermostat had run down and were flashing. No problem I thought. I inserted fresh batteries, made sure that the cool and fan settings were set and all I heard was a click from the ceiling unit overhead – as if it was trying to engage. Nothing else. Does this sound like an obvious fix? Did the fact that the batteries in thermostat which I kept at 78 powered-out for an unspecified period of time affect the unit? Does this sound like a complicated repair? Thanks again, any help is greatly appreciated.

    • Don Vandervort, HomeTips

      ZZyzx, you have a very unusual name…always the last on the list, I’ll bet :) I don’t think the batteries would cause this. If your outdoor unit won’t come on and and you hear a clicking noise followed by a soft hum or buzz your AC capacitor probably needs replacement. If you hear a click but no hum or buzz, the contactor—a relay to the compressor—probably needs replacement.

  • Carol Shellem

    Hello, have an issue with ac not cooling down home. Thermostat set at 77 and temp rises during the day to 81/ 82 degrees and never gets down to 77. until later at night. Lower the thermostat and still result during the day is the same although at night never gets lower than 77. Had sears tech today. Said system overcharged and adjusted to correct amount. On going issue. 3 ton carrier, 2003 install, 1550sq ft manu fact home and ceiling vents. Any Ideas, thanks

    • F Sager

      I am trying to find out if my ac is right size. It is 2.5 ton New Lennox installed in 2016. My house is 1,096 square feet. The air coming out of the compressor fan is cool and the unit does not cool my house below 84° even though the thermostat is set at 70°. I hope some of you might know what is wrong. Any ideas Greatly Appreciated.

      • Don Vandervort, HomeTips

        Generally speaking, you can multiply your square footage by 25 to get the proper BTUs needed for cooling. So 1096×25=27,400. Figure roughly 12,000 BTUs per ton. The math: 27,400/12,000= 2.28. So a 2.5-ton unit is about right. Looks to me like F. Sager’s is properly sized.

        Carol, your math is 1550×25=38750. Then, 38750/12000=3.29 so your 3 ton Carrier looks very slightly undersized, but should handle the jobs except in very high heat/humidity conditions. On those days, block heat gain with curtains, etc., keep the air moving with fans, and minimize using heat- and moisture-producing appliances during the day. Ultimately, you might need better insulation, etc.

        • F Sager

          Thank you for your time and effort in responding. Been reading many sites and believe I need to have the cfm and static checked by a HVAC Technician. Also need to get fan speed checked. There is NO sensation of feeling air coming out of the registers. That could be why my house heats up during the day and the AC cannot produce adequate air volume to cool the room in general.
          Thank you for your knowledge. Regards, Fred

  • helene otero

    Help I’m hot my ac is making a noise

    • Don Vandervort, HomeTips

      We’d like to help but can’t do much unless you give us a lot more detail.

  • Val

    Hi Don, we have a central air with a rooftop thermometer sadly during winter it is cooling and heats in summer (at least at the begging of the season) today the reading was 18 degrees (roof reading) and selecting 24 degrees inside still blew cold air! What could be the issue?

    • Don Vandervort, HomeTips

      Val, I’m not familiar with a rooftop thermometer…is this on a house or an RV? I can’t understand why an AC unit would be controlled by a thermometer that measures outdoor temperature. Please explain what is going on here.

  • Lauri Arnold

    The outside part of the ac is running, but I cannot hear the inside blower? Part running. When it gets hot in my house and the ac is not on, and the temp gets to 90degrees I hear a blower or fan running, sounds like the ac when it is on, now that happened today and so I turned on the ac and the blower/fan turned off. Do I need to replace the thermostat again or what should I check

    • Don Vandervort, HomeTips

      Please clarify. When you turn on the AC is the outdoor compressor running? Is the blower in the indoor air handler (or furnace) running and blowing air through the registers? Is the air cold? Does anything you do make the blower come on?

      • Lauri Arnold

        When I turn the ac on the outside compressor is running but the inside blower is not, not putting any air through the vents. I did read through other comments, checked the wiring in thermostat, changed the filter, the coils may have been frozen up, how do I check sooner next time? Because now everything seems to be working, it is an old unit and I usually don’t run it this much

      • Lauri Arnold

        Also the inside blower did not work when I tried turning on ac, but would turn on when the attic got hot and it automatically comes on to vent that out

    • Vijay S

      Something similar happened to me end of last week. I changed thermostat, but the problem with the blower did not go away. Next I changed the capacitor for the blower and that solved it. My capacitor is 10 micro-F. Old cap read 6.4 micro-F and that was the issue. I think this should be included as fix in the article above, but I do not see it.

  • Sam Feinberg

    My AC makes a humming sound when I turn the thermostat to cool, but it does not blow cool air right away. Instead, every couple of minutes it blows air for a few seconds. Any help would be much appreciated!

  • Chris Parent

    Hello, we last used the a/c in Aug of 2016 it was off over the fall/winter & spring) I tried turning it on this summer but no cool air. Here is what I did to try to remedy the situation…(after each step I tried running the a/c, I have the handler fan all the time. The outdoor A/C unit runs (fan and compressor turn on for a while, then they turn off after a few minutes) but I don’t get any cold air.
    1. Replaced the Thermostat batteries
    2. Cleaned the return air filters
    3. Cleaned the drain hoses/pipes.(some water is dripping when I remove the hose)
    4. Took off the shroud on the outdoor unit, cleaned, vacuumed, compressed air, rinsed with hose, power wash (using very wide tip so not to bend any fins).
    5. (with power off) disconnected and reconnected all spade terminals on capacitor & switching board, made a few fresh connections (cut, stripped and secured with wire-nuts)
    6. removed the capacitor, attempted to discharge it with a incandescent light bulb, (it appeared not to have any charge, it didn’t look bulging or leaking)
    7. Checked the resistance across the terminals (#’s went to 0 (or very close) then back to Open load), the same results occurred when I reversed the leads and retested (this advice from another website, suggests that the capacitor is Operational) [My multi-meter doesn’t measure capacitance]
    8. I checked to see if there was any pressure in the low side coolant line, (It measured “Good” on a gauge (like a tire pressure gauge but for coolant pressure on A/C units)
    9. I have attempted to examine the e-coil attached to the furnace, I was only able to peak at it from each side (because the intake and exhaust ABS pipes are in the way of completing removing the access panel) from what I could see, the coil is not caked up on the back side) I just attempted to access the front side of the coil from the cold air intake where the electrostatic filter is, all I could access was the blower motor.

    I am ready to call someone to take a look at it, as I have exhausted the steps I found that may help. Do you have any suggestions as to what I should try next?

  • Chance Stimson

    I just changed the capacitor and fan motor and with everything hooked up all I get is a buzzing sound. The fan won’t turn on. What could this be?

  • Steve

    So older 3 ton unit fan blower inside ok….outside 220VAC ok the relay outside comes in when you call for A/C but the fan on top of the compressor unit nor the compressor itself starts….just some low energy hum nothing like a stalled motor in locked rotor mode ……Both motor run capacitors are bad? Is that possible?

    • Pat McBride

      The outside condenser unit normally has on dual capacitor for both the compressor and the fan. It is very possible that the compressor part is faulty. It sounds like you have a bad capacitor, or a locked compressor. You need a tech or an electrician to check the capacitor..

  • Hugh R. Aukhundt

    My AC seems to be working but the air blowing is only cool. Set at 74 it runs continuously.. Indoor and outdoor fans work fine. Compressor outside is running (vibrating) as are the copper thin pipe and the insulated pipe. Both pipes are slightly cool. If I manipulate the thermostat it will turn on and off. A few drops of water from the indoor drain hose (not unusual.) Outdoor compressor (condensor??) gets hot (I can barely touch it). Could it be the capacitor or refrigerant.The unit is washed,clean and no obstructions. If you tell me it is the freon or coolant can I re-charge it myself?? Thank you in advance.

  • Mark

    I have a compressor unit outside and an attic evaporator/furnace/blower. Equipment and all ducts and vents were installed brand new 3 years ago. It has worked great and cooled the house well and fast.

    We’re converting it from a long-term rental to an AirBnB, so the unit has not been on much for a month. If there had been an obvious problem, I’m certain that the prior tenants would have complained quickly, loudly, and often. The system will now not cool the house below about 78. There is very little difference between the temp from the vents and the house temp. Called the guy who installed and told him the air wasn’t coming out very cold. All he did was rinse the coils outside, check the pressures, and then charge me. He said that once the unit dried off from his rinsing it would cool down. Same deal — 8 hours of run time and the temp went down 3 degrees. If pressures are OK and coils are clean, what else can it be? Time for a new service company? It’s hot!

  • r. purcell

    Central AC working but seems to take a long time to get to desired temperature. I checked temperature coming out of register & it’s only about 10 degrees less than room temperature. For example, if I set temperature at 75 degrees, air coming out of register is 65 degrees. What are possible reasons for why air coming out of register isn’t cooler?

    • Pat McBride

      60 to 65 is as cold as an AC can produce. What is the temp in your house? Not what you set the thermostat on, but the ambient temperature in the house. The discharge air out of the register nearest the furnace/ air handler should be approx. 18 degree difference.

  • Who’s that lady

    Okay our central air conditioner just started acting weird yesterday. When I came home it was making a slight humming noise throughout the house and I wasn’t sure what it was. Then the air flow reduced down to almost nothing as well as the coolness. We change the air filter and my husband also found out that there was Ice around the coils. We turned the fan on and the ice evaporated but then this morning when he woke up the ice reappeared. Does anyone have any suggestions as to what this could be.

    • Pat McBride

      Probably low on refrigerant.

  • Dan Wooten

    My AC was blowing warm air. I found that the breaker to the outside compressor unit was tripped. I reset the breaker and each time the thermostat called for cooling it would trip again. I changed out the capacitor and now the breaker no longer trips and the fan in the compressor unit turns on when the thermostat calls for cooling. However, the AC is still blowing warm air. I can’t tell if the compressor is running or not. Is there an easy way to tell this and/or to check if the compressor is bad? I figure the issue could be the compressor or no/low freon due to a leak. Is there anything else it could be? Is it possible that the problem could be a bad contactor, knowing that the fan is running (or does the fact that the fan is running tell you that the compressor should be getting power too, assuming that the wiring from the contactor to the compressor is good)?

    • The Anti Sheep

      Isolate it. Disconnect the power to the fan and see if you can hear the compressor turn on. That’s what I did.

  • Sha Col

    This morning it appeared the thermostat was not getting power. My husband checked the breaker and none were tripped but when he touched the breaker switch for the a/c I could here the outside unit come on and then immediately shut off. After a few times touching the breaker switch the thermostat registered power and the a/c finally came on and is currently cooling. Since there wasn’t power initially to the thermostat and the outside unit came on when the breaker switch was touched (not even switched) and immediately shut off does anyone know what could have been the issue which may actually lead to a real issue of having no a/c?

    • Pat McBride

      I would have that breaker checked, or just replaced. Per you description, it sounds like the breaker is defective. Get it checked right away.

  • rockybudgeboa

    Outside compressor comes on,. fan does not blow air inside. Problem started Saturday night. Called Enercare (We have a maintenance plan with them) Tech came and said it was Blower, a two second check confirmed that. Ordered part and it was installed Monday (Yesterday), all was well, AC was going for 10 hours then last night at 12:00 am, it happened again. Fed up and frustrated about this. Cannot afford a new system and ours is 12 years old. Someone, please help

    • Pat McBride

      Did the service man replace the blower motor without replacing the capacitor? The blower motor should not fail that soon and is under factory, or supplier warranty. Should not have to replace that unit if you have a qualified service tech. Most AC tech’s are not trained electricians, so make a lot of mistakes. Demand they fix it right or refund the cost of the blower motor. IMO

  • Steven B

    My evaporator coil was getting dirty all the time making my system freeze up every year or so. Found out my system needed a different size filter that was hard to find locally. My a/c guy installed something called a Filter Fitter that attached to my filter. I still buy the same size filter locally and this attaches to it. When the filter is dirty, I put it on the new one. This has worked well for me and my coil is clean on every check up.

  • Robert Hendrix

    I live in Harrisburg NC. and the inside humidity is staying in 65% range or higher in a new built 2500 sqft single floor home with AC on 72 deg. AC guy says the AC is functioning properly and the humidity is staying high since early June because a new home has a lot of humidity in the walls and wood flooring that needs to dry out before the inside humidity will drop to make the house feel more comfortable at a higher temp. What should the summertime inside humidity be in a home that only has 1 person most of the time and does NOT have a lot if in & out traffic. It is located with a Pond about 100 yards away. The AC guy said we needed to leave the temperature on 72 degrees all summer long to allow the AC “dry out? the moisture from the walls and flooring and cabinets of new home. Does this seem reasonable?

    • Pat McBride

      No. It doesn’t take that long to dry out the home. AC’s do work harder to remove humidity, but if it can do it within a 48 hour period, or less in most cases, then the AC is not functioning properly. You need another opinion. This man is not honest with you. IMHO.
      Take a temp reading of the ambient air in the home, and a reading from the closest discharge register to the air handler. There should be an 18 to 20 degreed diff. If you don’t have that, then the AC is not working correctly.

  • Nancy Ferran

    I have an large (don’t know the size) outside central air system. (It sounds like a helicopter, outside when it runs) I have a programmable thermostat. The unit turned on, cooled the house down to the programed temperature, but apparently never shut off. I came in about 1 1/2 hours after it should’ve shut off. It was not sounding right. It wasn’t as loud as normal. There is very little to no air coming out of the registers. I looked in my breaker box. There is no breaker labeled specifically for the a/c unit. I do have a box outside. I pulled what looked like it should be a series of small fuses. They looked like copper connectors, instead. I’ve tried turning the thermostat off and on several times. Once, even when I went outside to check the outside box. I put the thermostat to “cool” the unit turns on, but doesn’t produce any air. I have limited knowledge if the inner workings of a/c units. I, however, am willing to try to further diagnose/ fix the problem with detailed instructions, if someone is willing to provide them. I have just had to have roof repair done, so funds are very limited. I’d like to fix this, on my own, if possible.

    • Pat McBride

      Sounds to me like it ran too long and iced up the evaporator coil. (cooling coil) This would obstruct the air flow. And the cause could be a bad thermostat, or a shorted wire in the outside unit. I have seen mice chew the insulation off the thermostat wires and they will touch each other causing the compressor to run, but not the fan in the air handler. Another thing to look for is welded contacts in the outside contactor that starts the unit. It can cause the compressor and condenser fan to run, but not the evaporator fan in the home. . Is this a combination unit outside that has the air handler for the house and the condensing unit for the compressor all in the same housing? It could then be a capacitor that runs one fan that cools the condenser and moves the air into the house as well. There are many symptoms to diagnose without being there. Hope this helps, but can be very confusing without experience and understanding dialog.

  • w8onu60

    come home from vacation to a 90 degree house! capasitor is new, i just replaced that but don’t know where to look from here … where are coils ? to check if frozen .. is an outdoor Lennox unit

    • Pat McBride

      How did you surmise the bad capacitor? Curious. The evaporator is in the furnace unless you have an attic air handler. If this coil is frozen, then you either have dirty filters or a problem with the air handler blower not moving enough air. Could be a plugged coil as well if you didn’t keep the filters changed routinely. Also look for worn belt if you blower uses a belt. Most are hooked directly to the motor these days. It could also be low on refrigerant. Check ambient room temp and temp out of the nearest discharge register to the air handler. Should be an 18 to 20 degree diff.

  • Robert Gaston

    Hi, my emergency pan is very slowly filling with water. I blew out the main drain tube, dumpped some bleach down it which came out the other side so it is not clogged. I do not have a condensation pump, the drain is run off of gravity. The unit seems to not be cooling as well as it use to. What should be my next step in looking for what is causing the leak?

  • Melanie Hamby

    Hello, I had my entire ac system replaced 15 months ago and everything has been perfect up until about a month ago, when the display on my Honeywell non-programmable thermostat started going blank intermittently for no apparent reason – doesn’t require batteries, no loose wires behind the unit and otherwise works great. To rule out issues with the thermostat itself, I’ve bought a replacement and switched it out – didn’t resolve the problem. The ac works perfectly fine overnight and through the morning hours (will even feel a chill overnight) and there is no issue with hot air – the air is perfect cool; however, during the afternoon and early evening hours (hottest part of the day – in Florida), the system seems to be short cycling, and the house heats as high as 82 (thermostat set at 75). No odd noises, no dripping water, vent register is clear, no dirty filter, outside unit is clean and clear of debris, fan spins with no issues, no apparent issues with circuit breakers. Please give me some ideas of what the problem could be! Thanks!

  • Jorge Jaime

    Thursday night before Labor Day weekend. Come home from work to a 90F home and heat wave starts tonight! (112F-82F) Call an AC guy and he would come next day by 5pm and if the unit needs parts that he doesn’t have, Tuesday will be the day that the AC would work again. Not willing to melt over the long weekend, Mr Google brought me here. Read the steps and concluded that the controller board was the culprit.
    Unit was cold but blower not running, not humming and spinning freely when spun by hand. Checked capacitor (with a meter and the sparky way) anyways >OK
    Checked 24V and 120v feed to controller board > OK
    Some relays clicked but I guess the critical one wasn’t. They are sealed relays.
    Removed board and turned around to check the soldering points. One relay connection burned out,
    Cleaned the relay pin and board copper trace and re soldered.
    Resting now in my bed enjoying the AC working again : )

    ps. I will probably look for a replacement relay in the future

    • Kevin Johnson Stanley

      My AC in my house went out on Labor Day too & will only operate if I manually push the contacts in on the outside unit. I’ve replaced the fan motor, start capacitor, capacitor, contactor, & thermostat …. I’ve checked the voltage on each as well as the transformer in the attic system and all seems perfect. But I have to manually connect the contactor before the fan motor will operate and for the system to cool. The system will not cycle like this & continues to cool (very well), but what could this be that keeps the contactors from pulling in on their own?
      A friend of mine told me it may be the circuit board in my attic unit. This is the only other thing to replace other than the thermostat / transformer wires. Any thoughts / suggestions will be appreciated!! It’s hot here in Texas!

  • Kevin Johnson Stanley

    My AC in my house will only operate if I manually push the contacts in on the outside unit. I’ve replaced the fan motor, start capacitor, capacitor, contactor, & thermostat …. I’ve checked the voltage on each as well as the transformer in the attic system and all seems perfect. But I have to manually connect the contactor before the fan motor will operate and for the system to cool. The system will not cycle like this & continues to cool (very well), but what could this be that keeps the contactors from pulling in on their own?
    A friend of mine told me it may be the circuit board in my attic unit. This is the only other thing to replace other than the thermostat / transformer wires. Any thoughts / suggestions will be appreciated!! It’s hot here in Texas! kstanley3122@

  • kcsea

    below 32° neither heat pump nor furnace produces heat. is that a strip heat or emergency heat problem?

  • John Omasta

    I have a strange problem. I have 2 Gibson A/C units (3 yrs old). They will work fine for a few days, then the compressor on one or the other will suddenly not send cold coolant to the air handler, the copper pipe turns to room temp. There is no ice up condition and air flow is normal. If I turn off the A/C at the thermostat for a full day (or at least overnight – a couple hours does nothing), it starts working perfectly again. Any ideas??? PS: both thermostat’s have new batteries – that was already suggested and AC guy says coolant is correct level… of course when I put in a service call, he can’t come until the next day and it is working again – could I need 2 new thermostats? Both are Honeywell basic (not programmable) and they are 3 years old

  • Sue21165

    Central AC started acting up last night. This is what happens. The AC comes on and cools for about a half hour. After that time, the compressor (fan whatever you call it) keeps running, but no more cool air comes out; just air. Husband put a new filter in, but didn’t help. Each time we turn the AC on, it does the same thing. The AC is old. I don’t even know how old. We bought the home 6 years ago and it was here. We cannot afford a new AC and I don’t think we can afford to call someone to fix it. Any suggestions? HELP!

  • Al Witmer

    My outside unit responds to the thermostat setting but the fan in the indoor (furnace) will not turn on? Some times the indoor fan will run and blow cold air but it will only do so for about 5 minutes and then it shuts off again?

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