A/C Compressor Clutch (ECM Controlled)

To improve idle quality and wide open throttle performance, the A/C compressor is controlled by the ECM. A variable displacement (V5 type) system is used.

The system consists of a low pressure switch, high pressure cut-out switch, A/C power control relay, clutch control relay and compressor. Whenever system refrigerant pressure is adequate for operation, low pressure switch remains closed.

Low pressure switch is mounted in-line between the condenser and evaporator. A compressor-mounted high pressure cut-out switch is normally closed, but opens when head pressure gets too high. This disables the A/C clutch before excessive pressure damages system. A/C power control relay is actuated by the alternator.

When engine is running, power is supplied through the low and high pressure switches, to the A/C control relay. The ECM monitors this voltage and controls the relay ground circuit. This allows the ECM to increase idle speed before activating A/C clutch, and to disable A/C clutch during wide open throttle operation.