Air Delivery

Air Door Position Chart:

Air Delivery Vacuum Distribution:

The air valves in the Air Conditioning system are operated by electrical solenoids in the Heater/vent/Air Conditioning (HVAC) Programmer, and vacuum actuators located near the air valves. The solenoids are commanded "ON" or "OFF" depending on the mode selected at the HVAC Control Head. When a mode is selected at the Control Head a signal is sent to the Programmer over data lines (CKTs 835-A and 835-B). The Programmer then energizes the solenoid(s) which allows vacuum to go to the vacuum actuators, moving the air valves. A function of these is given below.

Air Mix (Temperature) Valve
The Air Mix (Temperature) Valve is mechanically linked to the Temperature Door Motor. This valve is controlled electrically instead of vacuum controlled. The valve is in the COOL position when a cold temperature is selected at the HVAC Control Head. This prevents air from blowing across the Heater Core. When a temperature other than cold is selected, the Air Mix Valve is open either partially or all the way, allowing some or all of the air to blow across the Heater Core.

Recirculation Valve
The Recirculation Valve is open in most of the operating modes permitting outside air to enter the Plenum. It is closed only in the "RECIRC" mode and at a temperature setting of 60°F. When closed, air from inside the vehicle is recirculated to get maximum cooling. Vacuum is applied to the actuator through a porous plug which resists air flow so that the actuator and valve will move slowly and will prevent cycling of the valve under borderline conditions of outside and recirculating air flow requirements.

Front And Rear Mode Valves
The Front and Rear Mode Valves determine whether air flows to the Heater Outlets or the A/C-Defrost Outlets, or both. The position of these valves is determined by the mode selected.

In the "AUTO" mode, the HVAC Programmer determines the position of the mode valves depending upon the existing heating and cooling requirements.

A/C DEFROST VALVE
The A/C Defrost Valve determines whether the air goes to the Defrost Outlets or the A/C Outlets. The valve will be in the position (position B) to allow air to flow through the A/C outlets when the "RECIRC," "VENT," "BI-LEVEL" or "A/C" modes are selected at the HVAC Control Head.

The A/C Defrost Valve will be in position (position A) to allow air to flow through the Defroster Outlets when "HEATER," "DEFROST" or "FRONT DEFOG" modes are selected.

If in the "AUTO" mode, the valve will be in position according to existing heating and cooling requirements.

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