Compressor Clutch: Description and Operation

A/C Compressor Clutch
With the engine running, battery voltage is applied to the A/C switch, the micro switch, the A/C triple pressure switch, and the coil of the A/C compressor relay. When you press the A/C switch or set the controls to defrost, battery voltage is applied to the electronic thermostat. The solid-state switch in the electronic thermostat closes, providing a path to ground for the thermo switch relay, with the fan control switch in any position except OFF. Voltage is also applied through the A/C triple pressure switch to the coil of the thermo switch relay. This closes the thermo switch relay contacts, applying battery voltage to the A/C ON input of the Powertrain Control Module (PCM). The PCM then provides ground for the A/C compressor relay. The A/C compressor relay contacts close, applying battery voltage to the compressor clutch through the closed contacts of the A/C thermo-switch. If either the A/C thermo-switch or A/C triple pressure switch opens, the compressor clutch disengages.