Air Delivery and Temperature Control

HEATER-A/C CONTROL
With the ignition switch in the RUN position, voltage is applied through FUSE 4 and circuit 41 to the heater-A/C control. The voltage from circuits 1199 and 1236 is varied from battery to approximately 1.5 volts by the temperature control potentiometer. The control assembly provides ground paths for the vacuum/electric solenoid through circuit 150 and the control switches.

VACUUM/ELECTRIC SOLENOID
The vacuum/electric solenoid contains the solenoid valves that control the mode valve actuators. There is one solenoid for each mode valve actuator. When the solenoids are de-energized, the valves vent the mode valve actuators, allowing the vacuum actuator to return to the vent position determined by a spring. Voltage is supplied to the solenoids through circuit 41 and Fuse 4 which is powered in the RUN position.

AIR INLET VALVE
The air inlet valve closes the outside air inlet so that air from the inside of the vehicle is recirculated through the A/C system for maximum cooling. The outside air inlet is closed when vacuum is applied to the actuator. When the air inlet valve actuator is vented, the spring returns the recirculation valve to position A, which allows outside air to be drawn into the vehicle.

AIR TEMPERATURE VALVE
The air temperature valve determines how much air flows through the heater core, which determines the temperature of the air to the outlets. It is moved by the electric actuator. The position of the valve is determined by the voltage level of the temperature control output from the heater-A/C control. The electric actuator is powered with the ignition switch in the RUN position. Voltage is applied through FUSE 4 and circuit 41.

OUTER MODE VALVE
The outer mode valve determines whether airflow will be directed to the I/P outlets or the heater/defrost outlets. With no vacuum applied to the actuator, the valve is in position A, which directs air to the heater/defrost outlet.

INNER AND OUTER MODE VALVE
The inner and outer mode valve is a small valve which allows partial airflow to the I/P outlets when the outer mode valve is in position A. The inner and outer mode valve is opened when vacuum is applied to the inner and outer mode valve actuator.

DEFROSTER VALVE
The defroster valve can assume three positions and is operated by a bi-directional vacuum actuator which can move the valve to either of two positions. If no vacuum is applied to either vacuum actuator, the valve is in midposition. Airflow with the valve in the midposition B will be delivered to both the defrost outlets at the windshield and the heater outlets at floor level. When the heater solenoid is activated, vacuum to the defroster valve actuator is supplied by the red vacuum hose and the actuator moves the valve to position C, forcing all airflow to the heater outlets. When the defrost solenoid is activated, vacuum to the defroster valve actuator is supplied by the blue vacuum hose and the actuator moves the valve to position A, forcing all airflow to the defrost outlets.