A central air conditioner that runs but doesn’t cool may just need to be cleaned. Plan to do this on a relatively warm day. First look for your owner’s manual and, if you can find it, follow its instructions. I f you can’t find it, request one from the manufacturer.
To clean the filter, remove it from the furnace or air handler (it’s usually located inside or very near the air inlet side). Replace a disposable filter or clean a reusable filter according to the manufacturers’ directions.
1) Before you begin, check the thermostat to make sure it is set to cool rather than heat. Then turn off the power to the unit; there is normally a shut-off or disconnect panel on the house wall next to the outdoor compressor. Otherwise, shut off the air conditioner’s 240-volt circuit at the main electrical panel.
2) Rake leaves and debris away from the outdoor condenser.
3) Remove any protective grille or cover from the condenser’s fins.
4) Use a soft brush to clean dirt and debris from the fins, then vacuum them with a brush attachment (be careful not to bend or damage them). If you accidentally bend fins, you can buy a comb made for straightening them at an appliance parts store.
5) Unscrew and lift the top grille off the unit, if possible. If the fan is attached to the grille, be careful not to pull any wires loose.
6) From inside the unit, hose out the fins (protect the wiring and motor with plastic). If your owner’s manual calls for lubricating the motor, do that now–don’t over-lubricate.
7) Then reassemble the unit.
8) To test it, turn the power on and set the thermostat to turn the unit on. Let it run for a few minutes, then feel the two pipes that connect to the condenser unit (slide any insulation back). One should feel warm, the other cool. Otherwise, call an air conditioning technician–the refrigerant may need to be recharged.
Note: Avoid straining an air conditioner’s compressor by waiting at least five minutes between turning it off at the thermostat and turning it back on.