Air Delivery and Temperature Control

Table #2 C36 And C34 Component State:

HEATER-A/C CONTROL
With the Ignition Switch in "RUN," voltage is applied through the IGN Fuse to the Heater-A/C Control. The operating mode of the system is determined by push button switches on the front panel. Output voltages determine which air valves are to be operated as well as the position of the Air Temp Valve.

VACUUM/ELECTRIC SOLENOID
The Vacuum/Electric Solenoid contains the solenoid valves that control the vacuum actuators. When the solenoids are de-energized, the valves vent the vacuum actuators, allowing the vacuum actuator to return to the "VENT" position.

RECIRC VALVE
The RECIRC Valve closes off the outside air inlet so that the air from the inside of the vehicle is recalculated through the A/C System for maximum cooling. The outside air inlet is closed when vacuum is applied to the actuator When the vacuum actuator is vented, the RECIRC Valves close off the in-car air inlet which allows outside air to be drawn into the vehicle.

AIR TEMP VALVE
The Air Temp Valve determines how much air flows through the Heater Core, which determines the temperature of the air to the outlets. It is moved by an electric motor which is part of the Electric Actuator. The position of the valve is determined by the voltage at output of the Temperature Lever in the Heater-A/C Control.

SLAVE VALVE
The Slave Valve determines whether air flow will be directed to the panel outlets. With no vacuum applied to the actuator, the valve is positioned to allow no air flow to the panel outlets.

UPPER VALVE
The Upper Valve determines whether air flow will be directed to the windshield defrost outlets. With no vacuum applied to the actuator, the valve is positioned to allow air flow to the windshield defrost outlets.

LOWER VALVE
The Lower Valve can assume three positions and is operated by a hi-directional vacuum actuator which can move the valve to either of two positions. If no vacuum is applied to either vacuum actuator, the valve is in midposition. Air flow with the valve in midposition will be delivered to the defrost outlets and the floor outlets. With vacuum applied to Lower Valve Actuator red vacuum hose, the valve is positioned to direct air flow to the floor outlets and slight air flow to the defrost outlets. With vacuum applied to the Lower Valve Actuator yellow vacuum hose, the valve is positioned to direct air flow to the defrost outlets and slight air flow to the floor outlets.

REAR TEMPERATURE VALVE
The Rear Temperature Valve is activated by vacuum originating from a "tee" in the Upper Valve vacuum line. With no vacuum applied, the Rear Temperature Valve routes air to the floor and window vents.

HEATER-A/C CONTROL VACUUM CONTROL SOLENOID VALVE (C36 AND C34 ONLY)
With the Ignition Switch in "RUN," voltage is applied to the Heater-A/C Vacuum Control Solenoid Valve through the IGN Fuse. In the de-energized state, vacuum is applied to port 1 of the Auxiliary Heater Water Shutoff Valve through the Heater-A/C Vacuum Control Solenoid Valve. When energized, the Heater-A/C Vacuum Control Solenoid Valve vents port 1 of the Auxiliary Heater Water Shutoff Valve. To energize the Heater-A/C Vacuum Control Solenoid Valve, the Auxiliary Blower Switch must be in the "OFF" position, or the Auxiliary Blower Control must be in the "OFF" position with the Auxiliary Blower Switch in the "RR CTRL" position. The Heater-A/C Vacuum Control Solenoid Valve may also be energized if the Heater-A/C Control is in the "OFF" position and the Auxiliary Blower Switch is not in the "OFF" position. During normal fan operation, the Heater-A/C Vacuum Control Solenoid Valve is de-energized.

AUXILIARY HEATER WATER SHUTOFF VALVE (C36 AND C34)
The Auxiliary Heater Water Shutoff Valve is a three-position two-vacuum port water valve that regulates coolant flow to the rear compartment heater core. Its three positions (Wide-Open, Restricted and Closed) are controlled by vacuum applied to ports 1 and 2 of the valve. The application of vacuum to these ports is controlled by the Heater-A/C Control Vacuum Control Solenoid Valve (port 1) and the Heater-A/C Control (port 2). When the Heater-A/C Control Vacuum Control Solenoid Valve is energized, port 1 of the valve is vented and port 2 is mechanically overridden, causing the valve to be in the Wide-Open position. This position is required for filling the cooling system. With the Heater-A/C Control in the "HTR-DEF" Mode ("OFF," "LOWER," "DEF," "MIX" [PONT] "DEFOG" [CHEVY, OLDS]) and the Auxiliary Blower Switch in an "ON" position, vacuum is applied to port 1 and port 2 is vented, causing the valve to be in the Restricted position, limiting coolant flow to the rear heater core. The Rear Vacuum Door will direct air to the floor and window vents. Placing the Heater-A/C Control in the "Upper" Mode ("RECIRC," "A/C," "UPPER," "BI-LEV"), both ports 1 and 2 have vacuum applied, causing the valve to be in the "CLOSED" position, preventing coolant flow to the rear heater core. Placing the Temperature select lever to within 30% of Full Cold Position, will also cause a "CLOSED" Position. The Rear Vacuum Door will route air to the overhead vents.