A window air conditioner can be a lifesaver during the summer months. The makings of an air conditioner are not too complicated, especially the little ones that sit in the window. Essentially these units consist of a fan, a compressor, some refrigerant and a power cord. When the AC unit starts acting up, it does so in a predictable pattern. By doing a little diagnosing, you can track down the problem and determine if it is worth repairing.
Check the most obvious first, the fuse. If the fuse is tripped, reset the breaker and turn the unit on again.
Let the air conditioner run to see if it will trip the fuse a second time. If so, check the circuit size to make sure it is adequate for the unit. You may have to install the air conditioner so that it can plug into a different outlet.
Check the power plug on the air conditioner if the fuse looks fine. Some units have a current interrupter on the cord to keep it from blowing the fuse. If the button is pushed outward, push it back in to reset it.
Attempt to turn on the AC. If it works this time, let it run to see if it will trip the interrupter again. If so, you still may have a circuit issue.
Other Things to Check
Turn the unit on to see if the fan is working. You should hear it blowing and feel air coming out of the front of the unit. If the unit sounds like it has started but you feel no air, the fan may not be turning.
Remove the front cover of the air conditioner. Place your hand on the compressor unit. One part of the compressor lies across the front of the unit, under the panel. It looks like a metal filter. If the compressor feels very hot, turn the unit off and allow the compressor to cool. While you are waiting, take out the vacuum cleaner and remove any debris and dust bunnies that have built up on the compressor unit.
Restart the unit in a few hours. As you do, listen for a clicking sound, which is an indication that the compressor is trying to start but cannot. The compressor motor is bad. If the compressor starts successfully but shuts down after a few minutes, the motor is not working correctly. A bad compressor motor signals the end of that air conditioner. Replacing the motor would cost more than a new air conditioner.
Feel the front of the unit. If it is blowing and you can hear the compressor running but the air is hot, refill the refrigerant.
Open the front panel and remove the filter. If everything seems to be functioning but the quality is lacking, the filter may need a good cleaning. Remove the filter, and wash it out in the sink. Cleaning the filter on a regular basis will help the unit function more efficiently.