Air Delivery and Temperature Controls

A/C Evaporator Core

All air passing through the A/C plenum moves across the A/C Evaporator Core. When the Compressor is on, the core cools and removes moisture from the air.

Inlet and Outlet Valves

The O/S Air-Recirc. Valve, A/C-Defrost Valve and Mode Valve are moved according to the position of the A/C Mode Selector. The Selector contains vacuum valves or switches. These valves apply and remove vacuum to Vacuum Actuators that move the inlet and outlet valves.
The O/S Air-Recirc. Valve is in position A for every A/C Mode Selector position except MAX. The actuator bellows are expanded which opens the O/S Air-Recirc. Valve and lets outside air into the module.
When the A/C Mode Selector is moved to MAX, vacuum is applied to the O/S Air Recirc. Valve Vacuum Actuator. The bellows are drawn in and the Valve is moved to position B. Air from inside the vehicle is pulled into the module.
The Heater-A/C Bi-Level Valve Vacuum Actuator, which controls the Mode Valve, can assume three positions. The Actuator is operated by two bellows and two vacuum switches. With the A/C Mode Selector in MAX, A/C, VENT or DEFROST, vacuum is applied through the WHT hose. The bellows closest to the WHT hose contract, moving the Valve to position A. Air flow is directed toward the windshield outlets or A/C-instrument panel outlets and no air flows from the floor outlets.
The Heater-A/C Bi-Level Valve Vacuum Actuator, has vacuum applied through the LT GRN hose with the A/C Mode Selector in LOWER. The bellows closest to the LT GRN hose contract. The Valve is pulled to position C. All air is directed to the floor outlets.
With the A/C Mode Selector in BI-LEVEL or OFF no vacuum is applied to either side of the Actuator, Both bellows expand part way. The Mode Valve moves to position B. Part of the air flows out the floor outlets. The rest of the air flows out the A/C-Instrument panel outlets.
The A/C Defrost Valve is controlled by the A/C Defrost Bi-Level Valve Vacuum Actuator. With the A/C Mode Selector in any position but OFF, LOWER, DEFOG, or DEFROST, vacuum is applied to the Actuator. The bellows contract and the A/C Defrost Valve is pulled to position B. All air flows out the A/C-instrument panel outlets.
With the A/C Mode Selector in OFF, LOWER, DEFOG or DEFROST, vacuum is removed from the A/C Defrost Valve Vacuum Actuator. The bellows extend and the Valve moves to position A. All air passes out the windshield outlets.

Temperature Valve Control

The in-vehicle temperature valve, located in the heater and A/C plenum is controlled by the A/C Temperature Valve Actuator. This actuator receives input from the Heater And A/C Control Assembly. The Temperature Control is tied to a variable resistance that sends a voltage signal to the A/C Temperature Valve Actuator. The voltage sent to the actuator varies with the position of the temperature control. When the A/C Temperature Valve Actuator receives a change in voltage to its temperature control input, it applies power to its Temperature Valve Motor. The motor moves the temperature valve to the selected position within the heater and A/C plenum. The Heater And A/C Control Assembly and A/C Temperature Valve Actuator receive power with ignition switch at RUN. The A/C Temperature Valve Actuator receives ground through the Heater And A/C Control Assembly.