Circuit Operation

CIRCUIT OPERATION

BLOWER MOTOR CONTROL
The Blower Motor is a variable speed motor. The higher the voltage applied to the motor, the faster the speed.

With the Ignition Switch in "RUN" and the Heater Control Assembly in "OFF," voltage is applied to the Blower Motor Low Speed Relay coil. The relay is energized and voltage to the Blower Switch is removed. No voltage is supplied to the Blower Motor.

When any other mode except "OFF" is selected, the Blower Motor Low Speed Relay is de-energized and voltage is applied to the Blower Switch and Blower Motor Resistor.

With the Blower Switch in "LO," voltage is applied through the Blower Motor Resistor and the Blower Motor High Speed Relay to the Blower Motor. The Blower Motor runs at low speed.

As the Blower Switch is moved through positions "M1" and "M2," the switch bypasses part of the Blower Motor Resistor, allowing more voltage to be applied to the Blower Motor, which will increase its speed.

When the Blower Motor Switch is in "HI," voltage is applied to the coil of the Blower Motor High Speed Relay. The Blower Motor High Speed Relay is energized removing the Blower Motor Resistor from the circuit. Battery voltage is then applied directly to the Blower Motor through the Blower Motor High Speed Relay contacts. The motor runs at maximum speed.

HEATER CONTROL ASSEMBLY
With the Ignition Switch in "RUN," voltage is applied through the CLUST Fuse to the Heater Control Assembly. The operating mode of the system is determined by push button switches on the front panel. Voltages from the Heater Control Assembly determine which air valves are to be operated as well as the position of the Air Temperature Valve.

SOLENOID BOX
The Solenoid Box 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 its rest position.

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. The Air Temperature Valve is moved by an electric motor which is part of the Air Temperature Valve Motor. Position of the valve is determined by the voltage level at the output of the Temperature Lever, in the Heater Control Assembly.

VENT VALVE
The Vent Valve determines whether air flow will be directed to the Vent 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 Vent Outlets when the Vent 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 midposition 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 air flow to the Defrost Outlets.