With Electronic A/C

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 when the air conditioning load should be removed from the engine, such as during full throttle.
Whether or not the A/C Compressor operates depends on both the particular mode selected at the Electronic A/C Control Assembly and the Control Assembly temperature setting.
When an A/C mode or DEFROST is selected, the Control Assembly provides a ground for the A/C Control Relay, closing the normally open contacts. If the A/C Pressure Cycling Switch and the A/C High Pressure Cutout Switch are both closed, battery voltage will be applied through the A/C Compressor Control Relay to the A/C Compressor Clutch. The A/C Compressor Control Relay is normally closed and opens when the Engine Control Module grounds the Relay coil. This occurs when the Engine Control Module determines that the A/C Compressor Clutch should be disengaged, such as under full throttle.
The Engine Control Module also receives an A/C request signal, telling it that the Electronic A/C Control Assembly has been placed in an A/C mode and both the A/C High Pressure Cutout Switch and the A/C Pressure Cycling Switch are closed. When the Engine Control Module sees this request signal, it will increase engine rpm to compensate for the increased load on the engine.
The A/C Pressure Cycling Switch disables the A/C Compressor Clutch if pressure in the system is too low. This situation arises when an A/C mode is selected when the ambient temperature is below approximately 6°C (45°F). The A/C High Pressure Cutout Switch disables the A/C Compressor Clutch if pressure in the A/C System is too high (above 2700 kPa [390 psi]).
The Electronic A/C Control Assembly also sets malfunction codes when a problem exists, such as a low Freon condition. When this occurs, the A/C Control Assembly will disable the A/C Compressor Clutch until the fault code is cleared. Always cheek for the presence of any malfunction codes before servicing the A/C System.