For 1990-2009 cars

The operation of the A/C compressor clutch is controlled by the the body control module and powertrain control module. 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 BFC 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.