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 the Compressor Clutch through the normally closed Evaporator Temperature Switch, the Low Pressure Cut-Out Switch and the High Pressure Cut-Out Switch.

The Evaporator Temperature Switch opens if the evaporator temperature drops low enough for freezing to begin. The Compressor Kick Down Relay opens at full throttle to aid in acceleration. The Low Pressure Cut-Out Switch opens if the refrigerant pressure drops low enough that operation of the A/C System would be likely to damage the Compressor. The High Pressure Cut-Out Switch opens if refrigerant pressure rises to a point that is too high for normal operation.

NOTE: Late production vehicles with automatic transmission use a Compressor Kick Down Relay to shut off the compressor at full throttle.

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.