Early Production

DESCRIPTION

The Compressor for the air conditioning system is belt-driven by the engine through the A/C Compressor Clutch. The Clutch allows the Compressor to be disengaged when air conditioning is not required or to remove the air conditioning load from the engine when needed.

OPERATION

Operation of the Compressor depends on the particular A/C Mode selected by the driver. When the A/C Mode Selector Switch is in MAX, NORM, BI-LEVEL or DEF, battery voltage is applied through Fuse 7 and A/C Control Head Selector Switch to the A/C Cut-Out Relay.

The path to the A/C Cut-Out Relay is through the Pressure Cycling Switch which is normally closed. The Pressure Cycling Switch opens if the refrigerant pressure drops low enough that freezing of the evaporator may take place. It closes again when the refrigerant pressure rises enough that additional cooling is required. In this way the A/C Compressor is cycled on and off to maintain the evaporator at a low temperature but without freezing condensate in the evaporator.

The A/C Cut-Out Relay is operated by the Engine Control Module (ECM). When the ECM receives the A/C ON signal the ECM grounds the A/C Cut-Out Relay, energizing the relay. When the Relay is energized, voltage is applied to the A/C Compressor Clutch through the closed contacts of the relay.

If the ECM determines that the engine load should be reduced, such as during full throttle, the ECM de-energizes the A/C Cut-Out Relay which removes voltage from the A/C Compressor Clutch, thus removing the A/C load from the engine.

The A/C High Pressure Cut-Out Switch is normally closed. It opens if refrigerant pressure becomes too high for normal operation.

The Compressor Clutch Diode connected across the terminals of the A/C Compressor Clutch provides a path for the current resulting from voltage spikes. The voltage spikes are generated by the collapsing magnetic field of the clutch coil each time the clutch is de-energized.