Air Delivery

The air valves and vents 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 valve which supplies vacuum to the Vacuum Actuators according to the operating mode selected by the driver.

Temperature Valve
The Temperature Valve is mechanically linked to the Mode Selector in the Heater-A/C and Rear Defogger 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 Mode Selector 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 cools 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 Mode Valve
The A/C-Heat Valve Vacuum Actuator, which controls the A/C-Heat Mode Valve, is bi-directional. The actuator is operated by two vacuum motors and two vacuum switches. With the Mode Selector in MAX and VENT, vacuum is applied through the YELLOW hose, moving the A/C-Heat Mode Valve to position A. Airflow is directed to the Instrument Panel Air Outlets with some air bleed to the Floor, Windshield and Side Window Outlets.

The A/C-Heat Valve Vacuum Actuator has vacuum applied through the RED hose with the Mode Selector in OFF HTR, BLEND and DEF. The A/C-Heat Mode Valve is then moved to position C. All air is directed to the Floor, Side Window or Windshield Air Outlets depending on Mode Selector position.

When the Mode Selector is in BI-LEV, neither vacuum motor is under vacuum and the A/C-Heat Valve Vacuum Actuator moves to position B. Air is then directed to the Floor, Instrument Panel and Side Window Air Outlets with some air bleed to the Windshield Air Outlets.

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, VENT, BI-LEV, or HTR, vacuum is applied through the LIGHT GREEN hose, moving the Heat-Defrost Valve to position A. Ail airflow is directed to the Floor Outlets with some air bleed to the Windshield and Instrument Panel Air Outlets.

The Heat-Defrost Valve Vacuum Actuator has vacuum applied through the BLUE hose with the Mode Selector in DEF The Heat-Defrost Valve is then moved to position C. Air flows out of the Windshield Air Outlets with some air bleed to the Floor, Instrument Panel and Side Window Air 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 the Floor Outlets and the Windshield Air Outlets.