If you are a do-it-yourself-er, one of the easiest repairs you can make yourself is replacing the contactor on an air conditioning (AC) unit. A contactor is an electrical component switch and is used to control the AC's thermostat and gives energy to the fan and compressor of the AC's outer condensing unit. The signal sent to a magnetic coil is energized by the metal contacts and is delivered when the AC unit is turned on and the thermostat temperature is set.