The control assembly in the Instrument Panel (IP) contains the following three controls:

The controls are lit when the headlamps are on. The IP panel lighting circuit provides voltage. The dimmer wheel on the headlamp switch controls dial illumination brightness.

An electric motor controls the temperature door. The motor positions the door based on the temperature knob location.

When the temperature control is in the BLUE (Cold) position, the air delivered by the heater system is unheated. When the temperature control is in the RED (Hot) position, all of the air passing through the heater module is heated before the air is discharged. Intermediate positions of the temperature control cause a mixture of heated and unheated air in order to provide increasingly moderate air temperatures.

As the temperature control moves away from the BLUE (Cold) position, the temperature valve moves away from the heater core in order to allow some air to flow through the heater core. The closer the temperature control moves toward the RED (Hot) position, the more the temperature valve turns away from the entrance to the heater core. This action increases the airflow through the heater core. Heating a greater portion of the total airflow in this manner causes a warmer discharge of air from the outlets.

When the temperature control is in the full RED (Hot) position, the temperature valve performs the following actions:

This method of temperature control provides a very rapid response to any change in temperature selection throughout the entire range when the engine is warmed up.

The mode control rotary knob operates a rotary vacuum switch. The rotary vacuum switch routes engine vacuum to specific hoses in the vacuum harness. These hoses control various vacuum actuators in the HVAC system. Each actuator operates an air valve (a hinged deflector) that routes airflow to the various outlets of the heater system.

The following positions are control knob positions:

The blower switch provides a choice of three blower speeds. The blower switch receives power through the HTR - A/C fuse in the fuse block when the ignition is in the ON position. In the various speed positions, the circuit continues through the heater wiring harness to the blower motor resistor assembly near the blower motor.

From the resistor assembly, the circuit passes to the blower motor terminal in order to operate the blower motor. A circuit passes from the blower motor terminal to the cowl panel sheet metal in order to complete the blower motor circuit to ground. The circuit is located near the blower assembly in the engine compartment.