Air Delivery and Temperature Control

The Air Delivery system consists of the Heater and A/C Control Head, a solenoid assembly, vacuum actuators and air valves. The function of these are described below.


HEATER AND A/C CONTROL HEAD

With the Ignition "ON," voltage is applied through the A/C Fuse to the Heater and A/C Control Assembly. The operating mode of the system is determined by switches on the front panel. Output grounds to the Heater and A/C Solenoid Assembly determine which air valves are to be operated.


HEATER AND A/C SOLENOID ASSEMBLY

The Heater and A/C Solenoid Assembly contains the solenoid valves that control the vacuum actuators. There is one solenoid for each vacuum actuator. When the solenoids are de-energized, the valves vent the vacuum actuators, allowing the vacuum actuator to return to the vent position determined by a spring.


TEMPERATURE VALVE

The Temperature Valve is controlled by the Temperature Lever 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 DEFROST VALVE

The A/C Defrost Valve is controlled by the A/C Defrost Valve Vacuum Actuator. When the Mode Selector is in "MAX," "NORM," "BI-LEVEL" or "VENT," vacuum is applied through the RED hose to the A/C Defrost Valve Vacuum Actuator. This pulls the A/C Defrost Valve to position B and prohibits air from entering the Defroster Outlet.

If the Mode Selector is in "HEATER" or "DEFROST," no vacuum is applied and the A/C Defrost Valve moves to position A, thereby forcing the air out the Defroster Outlet.

FRONT MODE VALVE

When the Front Mode Valve Vacuum Actuator receives vacuum (only in "HEATER" Mode) the Front Mode Valve is pulled to position B. This prevents any air from flowing to the A/C and Defroster Outlets and forces it to go to the Heater Outlets. In any other mode, the Front Mode Valve is in position A, blocking the Heater Outlets.


REAR MODE VALVE

The Rear Mode Valve is controlled by the Rear Mode Valve Vacuum Actuator. When the Mode Selector is in "MAX," "NORM," "VENT" or "DEFROST," vacuum is applied to the Rear Mode Valve Vacuum Actuator which moves the Rear Mode Valve to position A. This allows air to flow to both the A/C and the Heater Outlets. In any other mode, the Rear Mode Valve is in position B.


RECIRCULATION VALVE

The Recirculation Valve Vacuum Actuator has no vacuum applied for every Mode Selector position except for "MAX." The actuator bellows are expanded. The Recirculation 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 Recirculation 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 Plenum.


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.