A/C System - Manual

OPERATION
Blower Circuits
With the Ignition Switch in RUN, voltage is present at the Heater Control Assembly Blower Switch through the HEATER Circuit Breaker, the Blower Motor winding and the Blower Motor Resistor.

With the Blower Switch in any position but OFF, current flows through the HEATER Circuit Breaker, the Blower Motor winding, the Blower Motor Resistors and the Blower Switch to ground.

The Blower Motor runs at speed "1," "2," "3," or "4," depending on Blower Motor Switch position.

^ In position "1" current must pass through three dropping resistors, so the blower motor runs at a slow speed.

^ In position "2" current passes through two dropping resistors, and the blower motor runs faster.

^ In position "3" current passes through one dropping resistor, so the blower motor runs still faster.

^ In position "4" current bypasses all dropping resistors, so the blower motor runs at the fastest speed.

Compressor Circuits
Voltage is present at the [1][2]A/C Relay contacts at all times through the A/C fuse.

With the Ignition Switch in RUN, voltage is present at the [1][2]A/C Relay and WOT Cutout Relay coils through the REAR WIPER Fuse. Voltage is also present at the A/C-Heater Control Assembly A/C Switch through this fuse and the A/C ON Indicator bulb.

Pressing the A/C Switch causes its contacts to close, grounding the Clutch Cycling Pressure Switch and the A/C ON Indicator. Current flows through the REAR WIPER Fuse, the A/C ON Indicator, the A/C Switch and the Blower Switch to ground; the A/C ON Indicator illuminates. At the same time, current also flows through the [1][2]A/C Relay and the Clutch Cycling Pressure Switch to ground; the A/C Relay coil is energized.

With the [1][2]A/C Relay coil energized, the Relay contacts close, applying voltage to pin 10 of the EEC Module (A/C Demand input). Also, current flows through the A/C fuse, the A/C Relay contacts, the WOT Cutout Relay contacts and the A/C Clutch Field Coil to ground. The A/C Clutch Field Coil energizes and the A/C clutch engages; the A/C compressor runs.

The compressor runs until system low side pressure drops to about 24.4 psi, at which time the Clutch Cycling Pressure Switch contracts open, deenergizing the [1][2]A/C Relay. With the Relay deenergized, the A/C clutch disengages and the A/C compressor stops running.

The Clutch Cycling Pressure Switch opens and closes as low side pressure drops and rises to maintain the proper temperature at the evaporator core.

Under wide open throttle conditions, the EEC Module grounds pin 54 to energize the WOT Cutout Relay and interrupt current flow to the A/C Clutch Field Coil.