With Manual 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 the particular mode selected at the Heater and A/C Selector Switch.
When an A/C mode or Defrost is selected, battery voltage is provided through the Heater and A/C Selector Switch to the A/C Pressure Cycling Switch. 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 ECM grounds the Relay coil. This occurs when the ECM determines that the A/C Compressor Clutch should be disengaged, such as under full throttle.
The ECM also receives an A/C Request Signal, telling it that the Heater and A/C Selector Switch has been placed in an A/C mode and both the A/C Pressure Cycling Switch and the A/C High Pressure Cutout Switch are closed. When the ECM 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]).