Troubleshooting a Home AC Unit

• 1). Make sure there really is a problem. Begin by making sure the controls on your home AC unit are set to "cool", and that the temperature in the room is higher than the thermostat setting on the air conditioner. Use a portable thermometer to check the room temperature, being sure to place the thermometer right next to the air conditioning unit to get an accurate reading. To test the thermostat, set the temperature on the air conditioner to at least three or four degrees below the temperature on the room. Listen carefully for the fan to start.
  
  
• 2). If the fan is not running on the inside of your home, go outside and listen for the condenser on the outside of the window. If neither the condenser nor the fan is running, check to make sure power is flowing to the air conditioner. Unplug the unit and plug another appliance into the receptacle. If there is no power, a fuse may have blown or the circuit breaker that serves the outlet may have been tripped. Check the electrical box in your home for a blown fuse or a tripped circuit.
  
  
• 3). Check the filters on your air conditioning unit for dirt and debris. Consult your owner's manual for the location of the filters and carefully remove the filter cover. Depending on the design, you may need to unscrew the cover to get to the filter. In other models you may be able to simply snap open the filter drawer to remove and replace the filter. After the filter has been removed, use a flashlight to examine it for dirt and blockages. If you have a spare filter on hand, replace it with a fresh one. If no spare filters are available, carefully clean the filter and replace it.