All of the fuses to the unit will be checked, and the Freon in the system will be looked at to make sure it's an the right level. The wires will be examined, especially if the unit has been struck by lightening, to ensure that they haven't been burned. All of the vents will be looked at to see that they are clear of debris. Some outside units can have leaves and grass built up on the outside, preventing them from running properly. An AC repair service makes it easy to check out what might be wrong with the unit without taking it to the business. Most companies can repair the unit at your home.