Rear Blower Motor

The rear auxiliary blower motor controls operate by grounding the relay coils through the switch contracts. 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 available either directly or indirectly to the auxiliary blower motor. Because the auxiliary blower motor grounds at ground G400 through CKT 150 (BLK), the motor operates.

Battery voltage is available to the coils of the three auxiliary blower motor relays when the ignition switch is the RUN position or the START position. This voltage is available from RR HVAC fuse 12 through CKT 341 (BRN). Battery voltage for the auxiliary blower motor operation is available at all times to the contacts of the three auxiliary blower motor relays. When a relay coil grounds, current flow energizes the relay in order to apply operating voltage to the auxiliary blower motor.

Grounding the coil of the auxiliary blower motor low speed relay applies operating voltage in CKT 1176 (YEL) to the auxiliary blower motor resistor. Current flow is through both the resistors and then through CKT 1176 (YEL) to the auxiliary blower motor. The voltage drop through the two resistors limits the auxiliary blower motor to the lowest speed.

Grounding the coil of the auxiliary blower motor medium speed relay applies operating voltage in CKT 1072 (LT BLU) to the auxiliary blower motor resistor. Current flow is through only one of the resistors and then through CKT 1176 (YEL) to the auxiliary blower motor. The voltage drop through the single resistor allows the operation of the auxiliary blower motor 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 in CKT 1172 (YEL). Current flow bypasses the resistors in the auxiliary blower motor resistor. The full battery voltage allows the operation of the auxiliary blower motor at the highest speed.

For the passenger van, each of the three auxiliary blower motor relays grounds through either the front auxiliary HVAC control module or rear auxiliary HVAC control module. The front auxiliary HVAC control module is overhead above the Instrument Panel (IP). The rear auxiliary HVAC control module is overhead, immediately behind the front seats. Control through the front auxiliary HVAC control module overrides any control adjustments through the rear auxiliary HVAC control module. 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 position, the MED position, or the LOW position, the associated relay coil grounds directly through front auxiliary HVAC control module in CKT 150 (BLK) to ground G400. The ground path from the rear auxiliary HVAC control module to the heater and A/C control logic module is through CKT 77 (DK BLU). In the heater and A/C control logic module, the ground path is through a diode that is forward biased only when voltage is available from the rear auxiliary HVAC control module. From the heater and A/C control logic module, the ground path is through CKT 203 (LT BLU) to the front auxiliary HVAC control module. In the front auxiliary HVAC control module, the ground path is through the switch contacts that are closed only with the switch in the REAR CNTL position. From this point, the ground path to ground G400 is the same ground path for both modules.

Placing the front auxiliary HVAC control module or the rear auxiliary HVAC control module in the LO position grounds the coil of the auxiliary blower motor low speed relay through the wire for CKT 1926 (DK BLU) and CKT 60 (YEL). Placing the front auxiliary HVAC control module or the auxiliary HVAC control module in the MED position grounds the coil of the auxiliary blower motor medium speed relay through wire for CKT 1925 (RED) and CKT 63 (TAN). Placing the front auxiliary HVAC control module or the rear auxiliary HVAC control module in the HI position grounds the coil of the auxiliary blower motor high speed relay through the wire for CKT 1924 (WHT) and CKT 52 (ORN).

For the cargo van, the single rear auxiliary HVAC control module grounds the coils of the three auxiliary relays through CKT 150 (BLK) to ground G400. The cargo van's rear auxiliary HVAC control module is overhead, above the IP. Placing the rear auxiliary HVAC control module in the LO position grounds the coil of the auxiliary blower motor low speed relay through the wire for CKT 1926 (DK BLU) and CKT 60 (YEL). Placing the rear auxiliary HVAC control module in the MED position grounds the coil of the auxiliary blower motor medium speed relay through the wire for CKT 1925 (RED) and CKT 63 (TAN).

Placing the rear auxiliary HVAC control module in the HI position grounds the coil of the auxiliary blower motor high speed relay through the wire for CKT 1924 (WHT) and CKT 52 (ORN).