Compressor HVAC: Description and Operation

How the Circuit Works

The climate control unit controls the blower controls, air delivery, and A/C compressor controls automatically. With the ignition switch in ON (II), battery voltage is supplied through fuse 14. The control unit is grounded at G402.

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 climate control unit 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 climate control unit must be pressed to activate the A/C system.