Compressor Controls

COMPRESSOR CONTROLS
The Compressor for the Air Conditioning System is driven by the engine by means of a belt drive and the A/C Compressor Clutch. The Clutch allows the Compressor to be disengaged when Air Conditioning is not required. Power to the A/C Compressor Clutch is supplied by the HTR A/C Fuse.


The A/C Compressor Clutch Diode is connected across the terminals of the A/C Compressor Clutch. Whenever the clutch is de-energized, the magnetic field around it collapses, generating an induced voltage in the clutch coil. The Diode provides a path for the current resulting from the induced voltage so other circuit components are not damaged.

With the A/C-Heater Selector Switch in any mode except VENT or HEAT, voltage flows from the LT GRN (66) wire through the Low Pressure Switch, through the DK GRN (59) wire to the A/C Control Relay and the Engine Control Module (ECM), through the DK GRN (59) wire to the high pressure cutout switch.


The A/C Request signal to the ECM closes the A/C Cutout Switch in the ECM providing a ground through the DK GRN/WHT (459) wire to the A/C Control Relay. This energizes the A/C Control Relay. Voltage from the HTR A/C Fuse then flows through the closed contacts of the relay to energize the A/C Compressor Clutch.


The A/C Request signal to the ECM also increases engine idle speed.