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Central Air Conditioner Will Not Cool

On a hot day, it’s easy to tell when an air conditioner isn’t working right. But figuring out WHY your AC is not working is another story because an AC system has many working parts. So you must do a little detective work to pin down the symptoms in order to sort out and solve the problem.

Start asking these questions:

Is the thermostat working properly? If you have an electronic thermostat that isn’t displaying any information, its batteries may be dead, or it may be wearing out.  Please see Home Thermostat Troubleshooting & Repairs.

Does any of the AC equipment run? If you turn the thermostat to “Cool” and absolutely nothing happens, please see Central AC Not Working At All. This information will also guide you through checking the air handler, clearing the condensate drain, and checking the outdoor compressor.

Does the AC equipment run but fail to blow air? If you can hear the AC running but it isn’t blowing air, please see Air Conditioner Not Blowing Air.

Does the AC blow air that isn’t cold? This would indicate that the thermostat and the blower motor are operating, but the refrigeration system (outdoor compressor) is not working right or air isn’t circulating properly, usually because of dirty filters.

When was the last time you changed the AC filters? The chances are fairly good that you may just need to replace or clean the air filters. This is a job you should do at least twice a year.

Does the compressor need to be cleaned? The step-by-step information below outlines how to clean the compressor. Also, please see AC Not Cooling Well. Note: Changing the filters and cleaning the compressor will also increase the efficiency of the unit, saving energy.

If your central air conditioner will not cool but you can hear it running, it may just need to be cleaned. Whether or not this is the cause of the problem, it’s the first remedy to try. Plan to do this on a relatively warm day. Never use a power washer for this—it can damage the fins. The following are guidelines; always refer to your owner’s manual. Note: Always turn off the power before cleaning the unit.

This is the best video we found to give you a brief overview of the process. We like this video because it shows how to clean the unit from the inside—not how to simply wash-down the coils from the outside.

This video gives you a little more information about how to get the top off the compressor:

air conditioner will not cool©Don Vandervort, HomeTips

Turn off the circuit breaker that serves the AC compressor.


1Turn off the power to the AC unit. There is normally a shut-off or disconnect panel on the wall next to the outdoor compressor. Also shut off the air conditioner’s 240-volt circuit at the main electrical panel.

2Rake leaves and debris away from the outdoor condenser. Trim any bushes that might block airflow.

3Unscrew and remove protective grilles and the top cover or grille from the compressor. If the fan is attached to the grille, be careful not to pull any wires loose.


4Use a soft brush to clean dirt and debris from the fins, and then vacuum the fins with a brush attachment (taking care not to damage them).

5Use a hose and nozzle with a trigger grip to spray debris from the fins (from inside the unit). Protect the wiring and motor from water with plastic sheeting or a large plastic garbage bag. If your owner’s manual calls for lubricating the motor, do that now—but don’t over-lubricate.

6Reassemble the unit. Just reverse the disassembly steps given above.

HA2016 Air-Conditioners---Central

7To test it, turn the thermostat to OFF, reset the power at the disconnect next to the compressor and the main panel, and then set the thermostat to ON. To avoid straining an air conditioner’s compressor, wait at least five minutes between turning it off at the thermostat and turning it back on. Let it run for a few minutes, and then feel the two pipes that connect the condenser unit to the air handler (slide any insulation back). One should feel warm, the other cool.

air conditioner will not cool

Air conditioner technician checks refrigerant levels.

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

Call for free estimates from local pros now:

For more on maintenance tips, see Preparing Your Air Conditioner for Summer.

Air Conditioners - Central

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