Compressor HVAC: Description and Operation

How the Climate Control Circuit Works

The climate control unit controls the blower controls, air delivery, and A/C compressor controls either automatically or semi-automatically. The control unit receives battery voltage at all times through fuse 13. With the ignition switch in ON (II), battery voltage is supplied through fuse 3. The control unit is grounded at G401.

A/C Compressor Controls

Voltage is provided at all times to the A/C compressor clutch relay contacts through fuse 59. 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 59 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 also on.