A/C Compressor Clutch

On many models, PCM regulates operation of A/C compressor clutch through a PCM-controlled A/C compressor clutch relay. This allows the PCM to disengage the A/C compressor when compressor load on engine may cause driveability problems (i.e., during hot restart, idle, low speed steering maneuvers and wide open throttle operation), or if A/C refrigerant pressure drops or rises beyond normal operating levels.

Ignition voltage is supplied directly to the A/C compressor clutch relay. The Powertrain Control Module (PCM) controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near zero volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the PCM will set a DTC.

Refrigerant pressure sensing may be accomplished by monitoring high and low pressure switches or a pressure sensor which will register either high or low pressure levels. Power steering load is monitored through a power steering pressure switch. Hot restart is monitored through the coolant temperature sensor. For component application and related wiring, see appropriate article in AIR CONDITIONING & HEATING. For related wiring, see AIR CONDITIONING in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.