Heater With A/C

The Rear Blower Motor is controlled by either of two Rear Blower Switches when optional rear 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 Rear Blower Motor will operate from the Rear Blower Switch at the Rear Auxiliary Heater and A/C Control Module only when the Rear Blower Switch at the Front Auxiliary Heater and A/C Control Module is in the REAR position. Refer to Air Delivery and Ventilation for a description of the control priorities for the ventilation modes. Testing and Inspection

Battery voltage is supplied when the Ignition Switch is in RUN to Relay Coil Pin 5 of each of the three Rear Blower Relays through the BRN (341) wires. Battery voltage is also supplied when the Ignition Switch is in RUN to contact Pin 1 of each of the three Rear Blower Relays through the RED (542) wires. With the Rear Blower Switch at the Front Auxiliary Heater and A/C Control Module in OFF and with the Rear Blower Switch at the Rear Auxiliary Heater and A/C 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 Rear 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 Rear 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 Rear Blower Resistor through the YEL (1176) wire. Current flows through two resistors and to the Rear Blower Motor through the YEL (1172) wire. The motor operates at its slowest speed.

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

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

An illumination lamp is provided at each Heater and A/C Control Module to facilitate Switch operations. The lamps are powered by the Instrument Panel Dimming system described in Instrument Panel Dimming. Testing and Inspection