Air Delivery and Temperature Control

BLOWER MOTOR
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.


AUXILIARY BLOWER MOTOR
The Auxiliary Blower Motor is also a variable speed motor. 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 Auxiliary Blower Motor Relay is removed. No voltage is supplied to the Auxiliary 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 Auxiliary Blower Motor Relay. The Auxiliary Blower Motor Relay is energized and voltage is applied to the Auxiliary Blower Motor from the R BLW Fuse. The ground for the Auxiliary Blower Motor is controlled by the Auxiliary Blower Switch.

When the Auxiliary Blower Switch is in "LO" or "MED," voltage is applied through the Blower Motor, and all or part of the Auxiliary Blower Motor Resistor to ground. When the Auxiliary Blower Switch is in "HI," the resistor is bypassed, and the Blower Motor connected directly to ground to run at high speed.

HEATER CONTROL ASSEMBLY
With the Ignition Switch in "RUN," voltage is applied through the IGN 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 Temp 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 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. The Air Temp Valve is moved by an electric motor which is part of the Temperature Door Actuator. Position of the valve is determined by the voltage level at the output of the Temperature Lever, in the Heater Control Assembly.

PANEL VALVE
The Panel Valve determines if 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.

DEFR VALVE
The DEFR Valve determines if 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.

HTR/DEFR
The Heater/Defrost Valve can assume three positions and is operated by a bi-directional vacuum actuator which can move the door 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 at the windshield, heater outlets at floor level and window defrost outlets. When the HTR Vacuum Actuator (red vacuum hose) is operated, the valve is positioned to direct air flow to the heater outlets and slight air flow to the defrost outlets When the DEFR Vacuum Actuator (yellow vacuum hose) is operated, the valve is positioned to direct air flow to the defrost outlets and slight air flow to the floor outlets.