Rear Blower Motor

The rear Auxiliary Blower Motor controls operate by grounding the relay coils through switch contacts. Battery voltage from HVAC Fuse is available at all times to the normally open contacts of each of the three Auxiliary Blower Motor Relays. When one of the relays operates, voltage is applied either directly or indirectly to the Auxiliary Blower Motor. Since the Auxiliary Blower Motor is grounded at Ground G400 by the BLK (150) wire the motor operates.

Battery voltage is available to the coils of the three Auxiliary Blower Motor Relays when the Ignition Switch is in the Run or Start positions. This voltage is supplied from RR HVAC Fuse 12 through the BRN (341) wire. Battery voltage for Auxiliary Blower Motor operation is available at all times to the contacts of the three Auxiliary Blower Motor Relays. This voltage is supplied by the HVAC Fuse through the RED (542) wire) to the relays. When a relay coil is grounded, current flow energizes the relay to apply operating voltage to the Auxiliary Blower Motor.

Grounding the coil of the Auxiliary Blower Motor Low Speed Relay applies operating voltage on the YEL (1176) wire to the Auxiliary Blower Motor Resistor. Current flow is through both the resistors and then through the YEL (1172) wire to the Auxiliary Blower Motor. The voltage drop through the two resistors limits the Auxiliary Blower Motor to it's lowest speed.

Grounding the coil of the Auxiliary Blower Motor Medium Speed Relay applies operating voltage on the LT BLU (1072) wire to the Auxiliary Blower Motor Resistor Current flow is through only one of the resistors and then through the YEL (1172) wire to the Auxiliary Blower Motor. The voltage drop through the single resistor allows the Auxiliary Blower Motor to operate at a higher speed.

Grounding the coil of the Auxiliary Blower Motor High Speed Relay applies operating voltage directly to the Auxiliary Heater Blower Motor on the YEL (1172) wire. Current flow bypasses the resistors in the Auxiliary Blower Motor Resistor. Full battery voltage allows he Auxiliary Blower Motor to operate at it's highest speed.

For the Passenger Van, each of the three Auxiliary Blower Motor Relays may be grounded by either the Front Auxiliary HVAC Control Module or by the Rear Auxiliary HVAC Control Module. The Front Auxiliary HVAC Control Module is located overhead above the Instrument Panel. The Rear Auxiliary HVAC Control Module is located overhead right behind the front seats Control by Front Auxiliary HVAC Control Module overrides any control adjustments made at the Rear Auxiliary HVAC Control Module. It is only when the Front Auxiliary HVAC Control Module is in the REAR CNTL position that the Rear Auxiliary HVAC Control Module has control over the blower speed. With the Front Auxiliary HVAC Control Module in the HIGH, MED, OR LOW position, the associated relay coil is grounded directly by the Front Auxiliary HVAC Control Module through the BLK (150) wire to Ground G400.

When operating from the Rear Auxiliary HVAC Control Module, the ground path is routed through the Heater and A/C Control Logic Module and through the Front Auxiliary HVAC Control Module to Ground G400. The ground path from the Rear Auxiliary HVAC Control Module to the Heater and A/C Control Logic Module is through the DK BLU (77) wire. In the Heater and A/C Control Logic Module, the ground path is through a diode that is forward biased only when a voltage is available from the Rear Auxiliary HVAC Control Module. From the Heater and A/C Control Logic Module, the ground path is through the ET BLU (203) wire to the Front Auxiliary HVAC Control Module. In the Front Auxiliary HVAC Control Module, the ground path is through switch contacts that are closed only with the switch in the REAR CNTL position. From here, the ground path to Ground G400 is common for both control modules.

Placing the Front or Rear Auxiliary HVAC Control Module in the LO position grounds the coil of the Auxiliary Blower Motor Low Speed Relay through the DK BLK (1926)/ YEL (60) wire. Placing the Front or Rear Auxiliary HVAC Control Module in the MED position grounds the coil of the Auxiliary Blower Motor Medium Speed Relay through the RED (1925) 1 TAN (63) wire. Placing the Front or Rear Auxiliary HVAC Control Module in the HI position grounds the coil of the Auxiliary Blower Motor High Speed Relay through the WHT (1924)/OR (52) wire.

For the Cargo Van, the coils of the three relays are grounded by the single Rear Auxiliary HVAC Control Module through the BLK (150) wire to Ground G400. The Cargo Van's Rear Auxiliary HVAC Control Module is located overhead above the Instrument Panel. Placing the Rear Auxiliary HVAC Control Module in the LO position grounds the coil of the Auxiliary Blower Motor Low Speed Relay through the DK BLU (1926) / YEL (60) wire. Placing the Rear Auxiliary HVAC Control Module in the MED position grounds the coil of the Auxiliary Blower Motor Medium Speed Relay through the RED (1925) / TAN (63) wire. Placing the Rear Auxiliary HVAC Control Module in the HI position grounds the coil of the Auxiliary Blower Motor High Speed Relay through the WHT (1924) / ORN (52) wire.