For 1990-2009 cars

The operation of the A/C compressor clutch is controlled by the body control module (BCM) and powertrain control module (PCM). The BCM receives an A/C request signal from the heater A/C control assembly through circuit 66. The BCM then sends a class 2 serial data message to the PCM through circuit 1807. Power for the A/C compressor clutch relay is supplied by the A/C BCM fuse and circuit 439. When the PCM receives an A/C request message from the BCM, the PCM grounds circuit 459 allowing the A/C compressor clutch relay to engage. Ground for the A/C compressor clutch is supplied through circuit 450.