Air Door: Description and Operation

CIRCUIT OPERATION

The air valves in the HVAC system, with the exception of the Temperature Valve, are moved by vacuum actuators. Vacuum is applied to the actuators through the Mode Selector in the Heater-A/C and Rear Defogger Control Assembly. The Mode Selector consists of a rotary vacuum which supplies vacuum to the vacuum actuators, according to the operating mode selected by the driver.

Temperature Valve
The Temperature Valve is controlled by the temperature control in the Heater-A/C and Rear Defogger Control Assembly. With the control in "C," the valve is in the cold position. This prevents air from blowing across the Heater Core. With the control in any position but "C," the Temperature Valve is open. According to the control position, some or all of the air blows across the Heater Core.

A/C Evaporator Core
All air passing through the A/C Module moves across the A/C Evaporator Core. When the compressor is on, the core is cooled and removes moisture from the air.

Outside Air Valve
When the Mode Selector is moved to "MAX," vacuum is applied to the Outside Air Valve Vacuum Actuator. The bellows are drawn in and the valve is moved to position B. Air from inside the car is pulled into the A/C Module.

In any other position of the Mode Selector, no vacuum is applied and the vacuum actuator bellows are expanded. The Outside Air Valve is then in position A. This opens the Outside Air Inlet and lets outside air into the A/C system.

A/C-Heat Valve
The A/C-Heat Valve Vacuum Actuator, which controls the A/C-Heat Valve, is bi-directional. The actuator is operated by two bellows and two vacuum switches. With the Mode Selector in "MAX," "NORM" and "VENT" vacuum is applied through the YELLOW hose, moving the A/C-Heat Mode Valve to position A. Air flow is directed to the Instrument Panel Outlets with some air bleed to the Floor, Windshield and Side Window Outlets.

The A/C-Heat Valve Vacuum Actuator has vacuum applied to it through RED hose with the Mode Selector in "OFF" "HTR," "BLEND" and Defrost. The valve is then moved to position C and all air is directed to the Floor, Windshield or Side Window Outlets, depending on the Mode Selector position. When the Mode Selector is in "B/L", neither bellows is under vacuum and the A/C-Heat Valve Vacuum Actuator moves to the Mid-Position. Air is then directed to the Instrument Panel Air Outlets and the Floor, Windshield or Side Window Outlets, depending on the Mode Selector position.

Heat-Defrost Valve
The Heat-Defrost Valve Vacuum Actuator, which controls the Heat-Defrost Valve, is bi-directional. The actuator is operated by two vacuum motors and two vacuum switches. With the Mode Selector in "MAX," "NORM," "B/L," "VENT" or "HTR," vacuum is applied through the LT GREEN hose, moving the Heat-Defrost Valve to position A. All airflow is directed to the Floor and Side Window Outlets with some air bleeding to the Windshield Air Outlets.

The Heat-Defrost Valve Vacuum Actuator has vacuum applied through the BLUE hose with the Mode Selector in Defrost. The Heat-Defrost Valve is then moved to position C and all airflow is directed to the Windshield Air Outlets with some air bleeding to the Floor and Side Window Outlets.

When the Mode Selector is in "OFF" and "BLEND," neither vacuum motor is under vacuum and the Heat Defrost Valve Vacuum Actuator moves to position B. Air is then directed to both the Floor, Side Window and Windshield Air Outlets.