A/C System - Manual

OPERATION

Main Blower Motor
With the Ignition Switch in "ACC" or "RUN" and the A/C-Heater Control Assembly in any position except "OFF", battery voltage is applied to the Blower Motor. The Blower Motor Switch applies ground to the Blower Motor through the Blower Motor Resistor Assembly. The slower Motor Resistor Assembly is a resistance network that controls Blower Motor speed by controlling current to the motor.

Main A/C-Heater
The A/C-Heater System includes a control assembly (on the instrument panel), an evaporator blower housing assembly, a plenum assembly, air distribution ducts, and a condenser and compressor (in the engine compartment).
The A/C-Heater Control Assembly contains the Blower Motor Switch and function selector lever. The function selector lever controls the A/C-Heater Control Assembly and A/C-Heater Function Selector Vacuum Valve, which operate together to control system vacuum and electrical operation.
With the function selector lever in "NORM A/C", the A/C-Heater Control Assembly applies voltage to the A/C-Clutch Field Coil and Blower Motor circuits. The Clutch Cycling Pressure Switch cuts off power to the A/C Clutch Field Coil with low suction pressure to prevent evaporator icing.
The WOT Cutout Relay is energized by a signal from the EEC Module. This signal opens up the relay's contacts to stop compressor operation during WOT conditions. The EEC Module signals the Relay to open when the engine needs more power or overheats.
Other controls on the A/C-Heater Control Assembly move cables or are vacuum operated to adjust doors in the air distribution system. The seven-position Function Selector Vacuum Valve controls air flow to the floor, I/P and defrost outlets by routing the vacuum path to the appropriate vacuum actuator motor.
The A/C-Heater Function Selector Vacuum Valve selects inlet air from outside the vehicle (VENT, HEAT, NORM A/C) or recirculating inside air (MAX A/C) with a vacuum actuator that moves an air door.
The Temperature Control Lever moves a control cable connected to the Temperature Blend Door, which directs air flow through and/or around the Heater Core to obtain the desired discharge air temperature.

Auxiliary A/C-Heater Blower
The Blower circuit for the Auxiliary Heater and A/C Systems uses two Blower Switches. The Front Auxiliary Blower Motor Switch is part of the Main Front Control Assembly. This Switch has an "OFF" position, three speed positions and a "REAR" position. With the Front Auxiliary Blower Motor Switch in the "REAR" position, a ground path is completed to the Rear Auxiliary Blower Motor Switch. This allows rear seat control of the Auxiliary Blower Motor.
When the switch is moved to the "REAR" position, the Auxiliary Blower Motor is controlled by the Rear Auxiliary Blower Motor Switch in the auxiliary unit. The switch has an "OFF" position and four speed positions.
Both switches operate the same as the Main Blower Switch.