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 58. With the ignition switch ON (II), voltage is supplied to the relay coil through fuse 3.

With the ignition switch ON (II), the climate control unit grounds the A/C ON input of the PCM through the A/C pressure switch. The PCM then grounds the A/C compressor clutch relay coil. This energizes the coil, which closes the relay contacts and provides voltage through fuse 58 to the A/C compressor clutch. The clutch then engages and begins turning the compressor. By default, when the climate control system is on, the A/C is on.