Air Delivery and Temperature Controls

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 "COLD," the valve is in the "COLD" position. This prevents air from blowing across the Heater Core. With the control in any position but "COLD," 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 Vacuum Valve 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-HEATER VALVE

The A/C-Heater Valve Vacuum Actuator, which controls the A/C-Heater Valve, is bidirectional. 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 A/C Outlet with some heater bleed.

The A/C-Heat Valve Vacuum Actuator has vacuum applied to it through ORANGE hose with the Mode Selector in "OFF," "HEAT,"" BLEND" and "DEF." The valve is then moved to position C and all air is directed to the Heater Outlet. When the Mode Selector is in "BI-LEV," neither bellows is under vacuum and the A/C Heater Valve Vacuum Actuator moves to the Mid- Position. Air is then directed to the both the Heater Outlet and the A/C Outlet.

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," "BI-LEV," "VENT," or "HTR," vacuum is applied through the RED hose, moving the Heat-Defrost Valve to position A. All airflow is directed to the Footwell Air Outlets with some heater bleed.

The Heat-Defrost Valve Vacuum Actuator has vacuum applied through the GREEN hose with the Mode Selector in "DEF." The Heat-Defrost Valve is then moved to position C and all airflow is directed to the Windshield Air Outlets.

When the Mode Selector is in "OFF" and "BLEND," neither vacuum motors are under vacuum and the Heat-Defrost Valve Vacuum Actuator moves to position "B." Air is then directed to both the Footwell Air Outlets and the Windshield Air Outlets.