Heating and Air Conditioning: Description and Operation

HEATER AND A/C CONTROL ASSEMBLY

With the Ignition Switch in RUN, voltage is applied through the CLUST Fuse and PNK/BLK (750) wire to the Heater and A/C Control Assembly. The voltage from the LT BLU (733) wire is varied from Battery to approximately 1.5 volts by the Temperature Control Potentiometer. The Control Assembly provides ground paths for the Solenoid Box through the BLK (150) wire and the control switches.

SOLENOID BOX

The Solenoid Box contains the solenoid valves that control the Vacuum Actuators. There is one solenoid for each Vacuum Actuators 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. Voltage is supplied to the solenoids through the BRN (50) wire and the HVAC Fuse, which is powered in RUN.

RECIRCULATION VALVE

The recirculation valve closes the outside air inlet so that air from the inside of the vehicle is recirculated through the A/C system for maximum cooling. The outside air inlet is closed when vacuum is applied to the actuator. When the Recirculation Valve Vacuum Actuator is vented, the spring returns the recirculation valve to position A, which allows outside air to be drawn into the vehicle.

AIR TEMPERATURE VALVE

The Air Temperature Valve determines how much air flows through the Heater core, which determines the temperature of the air to the outlets. It is moved by the Air Temperature Valve Motor. The position of the valve is determined by the voltage level of the temperature control output from the Heater And A/C Control Assembly. The Air Temperature Valve is powered with the Ignition Switch in RUN. Voltage is applied through the CLUST Fuse and the PNK/ BLK (750) wire.

A/C VALVE

The A/C Valve determines whether air flow will be directed to the A/C Outlets or the Heater/ Defrost Outlets. With no vacuum applied to the actuator, the valve is in position A, which directs air to the Heater/Defrost Outlet.

BI-LEVEL VALVE

The Bi-Level Valve is a small valve which allows partial air flow to the A/C Outlets when the A/C Valve is in position A. The Bi-Level Valve is opened when vacuum is applied to the Bi-Level Valve Vacuum Actuator.

HEATER/DEFROST VALVE

The Heater/Defrost Valve can assume three positions and is operated by a Bi-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 mid position. Air flow with the valve in the mid position (B) will be delivered to both the Defrost Outlets at the windshield and the Heater Outlets at floor level. When the Heater Vacuum Actuator is operated, the valve moves to position (C), forcing all air flow to the Heater Outlets. When the Defrost Vacuum Actuator is operated, the valve is moved to position (A) which will force airflow to the Defrost Outlets.