Front Ventilation Controls

The Front Air Delivery and Temperature Controls are provided for vehicles with heating and air conditioning as well as for vehicles with heater alone. The heater only option's Heater Control Module operates similarly to the HVAC Control Module except that the A/C Push-button and Temperature Dial MAX Detent features are not provided for the control of the Recirculation Door. For vehicles with air conditioning and 7.4 Liter Gasoline Engines, an Auxiliary Cooling Fan is provided. Refer to Cooling Fan for more information. Radiator Cooling Fan Motor

The Front Mode Door Motor, the Front Temperature Door Motor, and the Recirculation Door Motor are powered by the BRN (141) wires when the Ignition Switch is in RUN. Grounding for the door motors is through the BLK (150) wires to Ground G202.The HVAC Control Module is powered when the Ignition Switch is in RUN by the BRN (141) wires. Grounding is through the BLK (150) wire to Ground G200 for the IP.

The HVAC Control Module's ventilation controls for the Front Mode Door and the Recirculation Door are disabled when the Module's Front Blower Switch is in the OFF position. With the Front Blower Switch in the HI, M2, M1, or LO positions, the ventilation controls are enabled. The Front Temperature Door is not dependent on Front Blower Motor operations and can be controlled as long as the Ignition Switch is in RUN.

The Mode and Temperature Doors are positioned in proportion to the variable voltage signal received from the HVAC Control Module. Adjusting the Temperature Dial at the HVAC Control Module adjusts a rheostat which provides a voltage signal proportional to the dial position. This voltage is carried on the LT BLU (733) wire to the Front Temperature Door Motor which then positions in response to the voltage signal. Adjusting the Mode Dial at the HVAC Control Module adjusts a rheostat which provides a voltage signal proportional to the dial position. This voltage is carried on the WHT (454) wire to the Front Mode Door Motor which then positions in response to the voltage signal.

The Recirculation Door is a two-position door and is in the Recirculation position only when the input DK GRN (1614) wire is grounded through the HVAC Control Module. For air conditioned vehicles with 7.4 Liter Gasoline Engines, the Recirculation Door is also grounded when the Auxiliary Cooling Fan A/C Pressure Switch operates the Auxiliary Cooling Fan. The door is normally in the Outside Air position but moves to the Inside Air position when the input wire is grounded. A LED on the HVAC Control Module is illuminated when the Recirculation Door is grounded through the HVAC Control Module.