Central Air Conditioner Troubleshooting & Repairs

clean air conditioner©Don Vandervort, HomeTips

A central air conditioning compressor, located outdoors, should be cleaned before every cooling season.

Save energy and money while making your home more comfortable with these DIY air conditioner repair techniques.

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In brief:

If your A/C doesn’t work at all, be sure it’s receiving power at the electrical panel, then check the thermostat settings. If the air conditioner runs but doesn’t cool well: 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 the power and the fan on, 4. Clean the condensate drain, 5. Check and clean the outdoor compressor.

In depth:

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.

In addition, if your central AC works but doesn’t cool well, you’re bound to use far more energy than necessary to keep your house cool.

Several different kinds of problems can occur with a central air-conditioning system.

For example, you may find your central AC :

• Doesn’t work at all
• Runs but does a poor job of cooling
• Allows dramatic changes in room temperature
• Drips or leaks water
• Makes strange noises

Although some central air conditioner repairs must be handled by a qualified air-conditioning repair person, in this article we’ll look at how you can handle simple repairs and maintenance yourself.

In addition, these two articles may be very helpful for the general care and maintenance of your air conditioner: Preparing Your Air Conditioner for Summer and How to Replace Furnace & AC Filters. The latter is a job that should be handled at least twice a year, before the heating and cooling seasons.

Central Air Conditioner Doesn’t Work At All

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

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

If your central air conditioner doesn’t go on automatically when the thermostat signals the need for cooling, it’s quite likely that the thermostat isn’t working properly or the unit is receiving electrical power. Before you do anything else, be sure the thermostat is set to COOL and its temperature setting is well below the ambient temperature.
Then do the following:

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 should be on a dedicated 240-volt circuit.

2Make sure the furnace power switch is turned on and that the outdoor condenser’s power switch, which is mounted on the outdoor unit, hasn’t been shut off. Also be sure the 240-volt disconnect next to the compressor, which is in a metal box usually mounted on the house wall, hasn’t been shut off.


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

3Turn off the power to the air conditioner and check the thermostat. Remove the thermostat’s cover from the base (usually by pulling straight out) and replace the batteries (if it has batteries). Replace the cover and wait 3 or 4 minutes and try the system again.

4If that doesn’t do the job, open the thermostat again 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 two wires together, turn the power back off and either call an air-conditioning technician or check the capacitor.

The capacitor 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. 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. 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. These types of capacitors are basically two capacitors in one, with both sharing the common leg.

Still not working? Please keep reading.

HA Air-Conditioners---Central

Air Conditioner Doesn’t Cool Well

If you can hear your central air conditioner running, but it doesn’t cool well, the problem can be caused by a couple of issues. The very first thing to do is make sure the filter in the air handler is clean so that it receives proper air flow.

1Turn off the power to the air conditioning unit.

2Remove the door on the front of the air-handler cabinet to give you access to 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.

4Clear 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 A/C won’t work. Water is also likely to puddle around the unit or even flood the area. To deal with condensate problems, please see Air Conditioner Leaks Water, below.

5Clean the outdoor compressor. For complete instructions, please see Air Conditioner Doesn’t Cool Well.

6Make 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 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 going, the unit has a faulty capacitor that must be replaced by an AC repair technician.

If none of these steps worked, the chances are pretty good that the coolant needs to be recharged by an air conditioning professional.

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

Air Conditioner Doesn’t Blow Air

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.
Here’s how to 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.


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. Finally, some fan motors and fans need oiling; some have sealed bearings. If recommended by your maintenance manual, oil the bearings according to the manufacturer’s directions.

© Mikael Damkier | Dreamstime.com

Air Conditioner Leaks Water

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. This water exits the air handler 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.

If water is dripping or pooling at the base of the air handler, it may be leaking from one of the plastic pipes or tubes that carry it, something may be blocking the water’s flow, or 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 drain pipe has a small safety float switch (see photo) connected to it. If the drain pipe 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 drain pipe.

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.

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 a ball float inside that rises with the water level, should start. If it doesn’t, it is stuck or broken. If it’s stuck, you should be able to disconnect it from the power and from the inbound tubes, disassemble the top, and clean it out thoroughly. If it’s quite old or broken, you’re probably better off replacing the 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.

HA Air-Conditioners---Central

Air Conditioner Makes Noise

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” (above) and refer to your owner’s manual.

If a direct-drive blower is squealing or making a grinding noise, shut off the unit and call an HVAC repair technician—the motor’s bearings are probably shot.

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 / Shutterstock.com

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

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.

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

 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

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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. [email protected]

  • 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: https://www.youtube.com/watch?v=gDgqLbq1jQw
    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! [email protected]

    • 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?

  • 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 pipe..it 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 http://www.hometips.com/repair-fix/thermostat-temperature-wrong.html, 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.

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