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, current flows from the A/C-Heater Selector Switch LT GRN (66) wire through the Low Pressure Switch and the DK GRN/WHT (459) wire to the A/C Control Relay terminal B and the Engine Control Module (ECM).


The A/C Request signal to the ECM closes the A/C Cutout Switch in the ECM providing a ground through the RED (458) wire at terminal C of 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 and the high pressure cutout switch to energize the A/C Compressor Clutch.


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