Compressor HVAC: Description and Operation

A/C Compressor Controls
Voltage is provided at all times to the A/C compressor clutch relay contacts through fuse 19. With the ignition switch in ACC (I) or ON (II), voltage is supplied to the relay coil through fuse 16.

With the ignition switch in ACC (I) or ON (II), the climate control unit grounds the A/C ON input of the ECM through the A/C pressure switch. The ECM then grounds the A/C compressor clutch relay coil. This energizes the coil, which closes the relay contacts and provides voltage through fuse 19 to the A/C compressor clutch. The clutch then engages and begins turning the compressor. Whenever the climate control system is on, the A/C is on.