Compressor Controls

CIRCUIT OPERATION
The compressor for the air conditioning system is belt driven by the engine through the Cornpressor Clutch. "be 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.

A/C mode and compressor 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 the A/C Fuse and A/C Control Head Mode Selector Switch.

Pressure Cycling Switch
From the Heater and A/C Control Assembly voltage is applied to the A/C Compressor Clutch through the Pressure Cycling Switch. The Pressure Cycling Pressure is normally closed but opens when refrigerant pressure drops below 172 kPa (25 psi). it closes again when refrigerant pressure rises enough so that additional cooling is required. This action causes the A/C Compressor to cycle on and off so that the evaporator temperature does not drop low enough to cause icing.

ECM and engine idle speed
When voltage is applied to the compressor clutch it is also applied to the ECM at terminal J on connector C2. The ECM will then increase the engine idle speed while the A/C Compressor Clutch is engaged.