I was called to a home for a service call because the air conditioner was not cooling. Upon arrival, I found that the unit was not producing any cool air. 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, so I replaced it. After replacing the air filter, the unit started producing cool air again. I tested the unit to ensure that it was working properly and left the customer with a working air conditioner.