With Air Conditioning

CLIMATE CONTROL ASSEMBLY
The climate control assembly has three control knobs:
^ The airflow control or function selector knob controls vacuum and electrical applications.
^ The temperature control knob, attached to the potentiometer, controls the position of the A/C electronic blend door actuator mounted on heater air plenum chamber.
^ The blower motor control knob, attached to the heater blower motor switch , provides four speeds of blower motor operation.

AIR FLOW CONTROL
Air flow control is accomplished in the following manner:
^ Primary control is through the function selector knob mounted on the A/C-heater function selector switch which is part of the A/C control.
^ The function selector knob has the following positions-OFF, MAX A/C, NORM A/C, VENT, FLOOR, MIX and DEFROST
^ The vacuum selector valve combines a vacuum selector valve with an internal electrical switch.
^ The vacuum selector valve directs source vacuum to various vacuum control motors. Refer to the Vacuum Control Diagram, System Airflow Schematic and Vacuum Control Chart. Electro-Vacuum Diagram
^ Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch.
^ The position of the function selector knob determines the manner in which the system will operate.
^ Each position of the selector knob is detented for positive engagement.

TEMPERATURE CONTROL
The temperature control operates in the following manner:
^ Temperature control of the manual A/C-heater system is determined by the position of the temperature control knob (between COOL and WARM).
^ This control knob is connected to a potentiometer mounted in the A/C control. This potentiometer is electronically connected to the A/C electronic blend door actuator that operates the A/C air temperature control door.
^ The A/C electronic blend door actuator contains a reversible electric motor, another potentiometer and a printed circuit board. The wiper of the potentiometer is connected to the actuator output shaft and moves with the output shaft to indicate the position of the A/C air temperature control door.
^ Battery voltage is applied to the ends of each potentiometer. The voltage available at each wiper indicates the position of the potentiometer. The printed circuit board drives the actuator in whichever direction is necessary to make the actuator wiper voltage agree with the control wiper voltage.

System uses a reheat method to provide conditioned air to the passenger compartment.
^ All airflow from the blower motor passes through the A/C evaporator core housing, where it can be cooled and dehumidified.
^ Temperature is then regulated by reheating a portion of the cooled dry air and blending it with the remaining cool air to the desired temperature.
^ Temperature blending is varied by the A/C air temperature control door, which regulates the amount of cooled air that flows through and around the heater core, where it is then mixed and distributed.

BLOWER MOTOR CONTROL
Blower motor operation is controlled by the heater blower motor switch.
^ The heater blower motor switch provides four manually-selected blower speeds and may be operated in any position to select the desired amount of airflow.
^ The heater blower motor switch and the heater blower motor switch resistor assembly are electrically located in the ground circuit of the blower motor.

VACUUM HOSES
A vacuum hose harness, which is attached to the back of the A/C-heater function selector switch, directs vacuum to three doors in the manual system:
^ a [1][2]heater air damper door
^ a [1][2]windshield defroster door
^ a heater and A/C air inlet duct door

The speed control vacuum reservoir is used to store engine-produced vacuum needed to operate the vacuum control motors.
^ It is located on the LH wheel housing.
^ An A/C vacuum check valve prevents accumulated vacuum from returning to the engine.