Heating and Air Conditioning: Description and Operation

The air valves and vents in the Air Conditioning System are operated by mechanical and vacuum controls. There are no electrical circuits.

Temperature Valve

The Temperature Valve is mechanically linked to the Temperature Selector in the Heater-A/C Control Assembly. With the Temperature Selector at COLD, the Temperature Valve is in the COLD position. This prevents air from flowing across the heater Core. With the Temperature Selector in any other position, some or all of the air flows 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 Outside Air Valve 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 Module.

A/C-Heater Valve

The A/C-Heater Valve Vacuum Actuator, which controls the A/C-Heater 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, moving the A/C-Heater Valve to position A. All air flow is directed to the A/C Outlet.
The A/C-Heater Valve Vacuum Actuator has vacuum applied through the RED hose with the Mode Selector in OFF, HEATER, or DEF. The valve is then moved to position C and all air is directed to the Heat Outlet and Side Window Air Vents, or to the Defrost Vents.
When the Mode Selector is in BI-LEV, neither bellow is under vacuum and the A/C-Heater Valve moves to the middle position. Air is then directed to both the Heat Outlet and the A/C Outlet.

A/C-Defrost Valve

The A/C-Defrost Valve is controlled by the A/C-Defrost Valve Vacuum Actuator. Vacuum is applied to the actuator in all modes except DEF. With vacuum applied, the A/C-Defrost Valve moves to position B and all air flow is directed to the Heat Outlet. In the DEF mode, the valve moves to position A and air is directed to the Defrost Vents.