Auxiliary - Heater With A/C

The Auxiliary Blower Motor is controlled by either of two Auxiliary Blower Switches when optional auxiliary heating and air conditioning is provided. Both switches are located in overhead modules, one over the Instrument Panel and the other in the center of the vehicle. The Auxiliary Blower Motor will operate from the Auxiliary Blower Switch at the Auxiliary HVAC Control Module only when the Auxiliary Blower Switch at the Front Auxiliary HVAC Control Module is in the REAR position. Refer to HVAC Air Delivery and Temperature Controls for a description of the control priorities for the ventilation modes.

Battery voltage is supplied when the Ignition Switch is in RUN to Relay Coil Cavity 5 of each of the three Auxiliary Blower Relays through the BRN (341) wires. Battery voltage is also supplied when the Ignition Switch is in RUN to contact Cavity 1 of each of the three Auxiliary Blower Relays through the RED (542) wires. With the Auxiliary Blower Switch at the Front Auxiliary HVAC Control Module in OFF and with the Auxiliary Blower Switch at the Auxiliary HVAC Control Module in OFF, no grounding path is provided for the Relay Coils and the relays remain de-energized. The relay contacts remain open and no voltage is supplied to the Auxiliary Blower Motor.

When the Ignition Switch is in RUN and the Blower Switch at the Front Module is in LO, a ground path is provided for the Auxiliary Low Blower Relay through the DK BLU (1925) wire to the Front Blower Switch, then through BLK (150) wire to Ground G400. The Relay Coil energizes and the relay contacts close. This applies Battery voltage to the Auxiliary Blower Resistor through the YEL (1176) wire. Current flows through two resistors and to the Auxiliary Blower Motor through the YEL (1172) wire. The motor operates at its slowest speed.

When the Auxiliary Blower Switch at the Front HVAC Control Module is in REAR and the Auxiliary Blower Switch at the Auxiliary HVAC Control Module is in LO, the grounding path is different. The ground path is through the DK BLU (1925) wire to the Auxiliary HVAC Control Module The DK BLU (77) wire continues the ground path to the Auxiliary and HVAC Control Logic Module. ORN (77) wire continues the ground path to the Front Auxiliary HVAC Control Module where is continues to Ground G400.

When the Auxiliary Blower Switch is in MED, the Auxiliary Medium Blower Relay is energized. Current flows to the motor through one resistor and the motor operates at an intermediate speed. When the Auxiliary Blower Switch is in HI, the Auxiliary High Blower Relay is energized. Current bypasses both resistors and the motor operates at its highest speed.

An illumination lamp is provided at each HVAC Control Module to facilitate Switch operations. The lamps are powered by the Instrument Panel Dimming system.