Air Delivery and Temperature Controls

CIRCUIT OPERATION

The air doors and vents in the Air Conditioning System are operated by mechanical and vacuum controls. There are no electrical circuits. The functions of the air doors and A/C Evaporator Core are described below.


Heater Water Valve

The Heater Water Valve is operated by the Heater Water Valve Vacuum Actuator. Vacuum is applied to the actuator only when the Temperature Selector Lever is in the full COLD position. The valve closes, blocking the flow of hot water to the Heater Core.

When the Temperature Selector Lever is not in the COLD position, vacuum is removed from the actuator. The Heater Water Valve opens and hot water flows to the Heater Core.

A/C Evaporator Core

All air passing through the A/C Module moves across the A/C Evaporator Core. When the A/C Compressor is on (BI-LEVEL, NORM, MAX and DEF, the core is cooled, which removes heat and moisture from the air.


Air Doors


The Recirculating/Outside Air Door, Heat/Defrost Door, Upper Mode Door, and Lower Mode Door are moved according to the position of the Mode Selector. The Mode Selector contains vacuum valves or switches. These valves apply and remove vacuum to vacuum actuators that move the air doors.


Temperature Door

The Temperature Door is controlled by the Temperature Selector Lever in the A/C Control Head. With the lever in COLD, the door is in the COLD position. This prevents air from blowing across the Heater Core. With the lever in any other position, some or all of the air blows across the Heater Core.


Recirculating/Outside Air Door

When the A/C Mode Selector is moved to MAX, vacuum is applied to the Outside Air Vacuum Actuator. The bellows are drawn in and the door is moved to position B. Air from inside the car is pulled into the A/C Module.

In any other Mode Selector Switch position, the actuator bellows are expanded and the door is moved to position A. Air is drawn in from the outside.

Upper and Lower Mode Doors

The two Mode Doors determine the amount of air flow to the Instrument Panel Air Outlets. When the Mode Selector Switch is in MAX, NORM or VENT, vacuum is applied to both the Upper and Lower mode Vacuum Actuators.
Both doors then move to position B and all air flows out the Instrument Panel Air Outlets. In the BI-LEVEL mode, vacuum is applied only to the Lower Mode Vacuum Actuator which moves the Lower Mode Door to position B. The Upper Mode Door moves to position A. In these positions some air flows out of the Instrument Panel Air Outlets and the rest flows out of the Footwell Air Outlets. In HEATER, DEF and OFF, no vacuum is applied to either Vacuum Actuator and both doors move to position A.All air then flows to either the Footwell Air Outlets or the Windshield Air Outlets, depending on the position of the Heat/Defrost Door.


Heat/Defrost Door

With the Mode Selector Switch in OFF, BI-LEVEL or HEATER, vacuum is applied to the Heat/Defrost Vacuum Actuator. The bellows contract and the Heat/Defrost Door moves to the B position. Most of the air flows out of the Footwell Air Outlets. In all other positions of the Mode Selector Switch, no vacuum is applied to the Vacuum Actuator and the Heat/Defrost Door remains in position A, forcing most of the air out of the Windshield Air Outlets.