Air Delivery and Temperature Controls

The air valves and vents in the air conditioning system are operated by mechanical and vacuum controls. There are no electrical circuits. The functions of the plenum valves and A/C Evaporator Core are described below.


TEMPERATURE VALVE

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


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 or VENT, vacuum is applied through the YELLOW hose. The bellows closest to the YELLOW hose contract pulling the A/C-Heat Valve to position A. No air flows from the Floor Outlets with some heater bleed.

The A/C-Heat Valve Vacuum Actuator has vacuum applied through the RED hose with the Mode Selector in OFF, HTR, or DEF. The bellows closest to the RED hose contract. The A/C-Heat Valve is pulled to position C. All air is directed to the Floor Outlets.

With the Mode Selector in B/L (position 4), no vacuum is applied to either side of the A/C-Heat Valve Vacuum Actuator. Both bellows extend part way. The A/C-Heat Valve moves to position B. Part of the air flows out the Floor Outlets. The rest of the air flows out the Panel Outlets.


HEAT-DEFROST VALVE

The Heat-Defrost Valve is controlled by the Heat-Defrost Valve Vacuum Actuator. With the Mode Selector in any position but DEF (position 7), vacuum is applied to the actuator. The bellows contract and the Heat-Defrost Valve is pulled to position B. All air flows out the Floor Outlets with some defrost bleed.

No vacuum is applied to the Heat-Defrost Valve Vacuum Actuator with the Mode Selector in DEF. The bellows extend and the Heat-Defrost Valve moves to position A. All air passes out the Windshield Outlets with some heater bleed.


OUTSIDE AIR VALVE

The Outside Air Valve Vacuum Actuator has no vacuum applied for every Mode Selector position except MAX (position 2). The actuator bellows are expanded. The Outside Air Valve is in position A. This opens the Outside Air Inlet and lets outside air into the plenum.

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 plenum.


A/C EVAPORATOR CORE

All air passing through the Heater and 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.