I was called to a home to check on an air conditioner that was not running properly. Upon arrival, I found that the unit was not producing any cool air. I checked the unit and found that the compressor was not running. I checked the power supply and found that it was working fine. I checked the thermostat and found that it was set to the correct temperature. I checked the air filter and found that it was dirty. I cleaned the air filter and the unit started running again. The customer was very happy with the service and thanked me for my help.