A/C Compressor Clutch Relay

The PCM controls the A/C compressor clutch through a relay. This allows the PCM to receive an A/C select signal when driver moves mode lever into A/C position. The PCM also receives a request signal from the A/C temperature control thermostat (evaporator switch).

The PCM then adjusts idle speed using the IAC motor. Only then can the PCM activate the A/C compressor clutch through the A/C compressor clutch relay. The increased idle speed will compensate for the additional load caused by the A/C compressor.

On Cherokee with 4.0L engine, whenever the A/C compressor clutch is energized, the PCM also energizes the radiator (cooling) fan relay. This occurs regardless of engine coolant temperature.