A/C Compressor Controls

When the Ignition Switch is in RUN, battery voltage is applied through Fuse 20 to the A/C Select Switch on the A/C Control Panel. When the A/C Select Switch is pressed voltage is applied to terminal 3 of the Evaporator Temperature Regulator. The Evaporator Temperature Regulator applies voltage from terminal 2 to the Compressor Clutch through the High Pressure Cut-Out Switch, the Low Pressure Cut-Out Switch, the A/C Temperature Switch, and the Compressor Oil Temperature Switch.

The High Pressure Cut-Out Switch opens if refrigerant pressure rises to a value which is too high for normal operation. The A/C Temperature Switch opens to remove the Compressor load from the engine if the engine coolant temperature rises above 108°C (226°F). The Evaporator Temperature Sensor signals the Evaporator Temperature Regulator to deenergize the Compressor Clutch when evaporator temperature is low enough that freezing may result. The Compressor Oil Temperature Switch opens at 150°C (302°F) to protect the compressor.

Clutch Diode
Whenever the Compressor Clutch is de-energized, the collapsing magnetic field induces a voltage in the winding. The Clutch Diode provides a path for the resulting current.