A/C Compressor Controls

When the Ignition Switch is in RUN, battery voltage is applied through Fuse 20 to the Compressor Enable Switch. This Switch is located in the A/C Control Panel and is closed when either the center or lower slide levers are moved about 1/4 of the distance away from the left position. This ensures that the A/C Compressor does not run unless there is enough air flow to prevent freezing of the evaporator.

When the A/C Select Switch on the A/C Control Panel is pressed and the Compressor Enable Switch is closed, 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, 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 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.