A/C Clutch Relay Operation

THEORY OF OPERATION:
The A/C compressor clutch relay controls the 12 volt source for the A/C clutch. The relay is located in the power distribution center. One side of the relay control coil is supplied with 12 volts when the ignition switch is turned to the run position. The circuit is completed when the other side of the relay coil is grounded by the powertrain control module (PCM). When A/C is requested, the PCM adjusts the idle speed to accommodate the A/C compressor load on the engine. The PCM grounds the relay control circuit after the PCM receives an A/C request and adjustment of the idle speed has been implemented.

Fig. 22 Power Distribution Center (PDC):

AIR CONDITIONING CLUTCH RELAY-PCM OUTPUT
The PCM controls the air conditioning clutch relay ground circuit. Buss bars in the Power Distribution Center (PDC) supply voltage to the solenoid side and power side of the relay. When the PCM receives an air conditioning input, it grounds the A/C compressor clutch relay and the radiator fan relay.

When the PCM senses low idle speeds or wide open throttle through the throttle position sensor, it removes the ground for the A/C compressor clutch relay. When the relay de-energizes, the contacts open preventing air conditioning clutch engagement. Also, if the PCM senses a part throttle launch condition, it disables the A/C compressor clutch for several seconds.

The air conditioning clutch relay is located in the PDC. The inside top of the PDC cover has a label showing relay and fuse location.