With Manual A/C
CIRCUIT OPERATIONWhen the A/C Mode Selector Switch is in MAX, NORM, BI-LEVEL, or DEF, and the refrigerant level is adequate, the Compressor Clutch will engage the compressor.
The Pressure Cycling Switch turns the compressor off when the evaporator temperature is low enough to cause icing. It opens when the refrigerant pressure is less than 172 kPa (25 psi). This opens the circuit to the A/C Compressor Clutch. This switch also closes to cycle the compressor on again when the evaporator temperature and pressure rise enough to require more cooling.
It will open if the refrigerant pressure becomes too low.
The ECM receives a voltage input signal when the Compressor Clutch is engaged. The ECM turns on the engine cooling fans and increases the engine idle speed when the compressor is on.