Compressor HVAC: Description and Operation

How the Circuit Works

A/C Compressor Controls

Voltage is provided at all times to the A/C compressor clutch relay contacts through fuse 1. With the ignition switch ON (II), voltage is supplied to the relay coil through fuse 14.

With the ignition switch ON (II), the heater control unit-panel grounds the A/C ON input of the ECM/PCM through the A/C pressure switch and the multiplex control unit. The ECM/PCM then grounds the A/C compressor clutch relay coil. This energizes the coil, which closes the relay contacts and provides voltage through fuse 1 to the A/C compressor clutch. The clutch then engages and begins turning the compressor.

The A/C button at the heater control unit-panel must be pressed to activate the A/C system.