The rear auxiliary blower motor controls operate by grounding the auxiliary blower motor relays through the switch contacts. Battery voltage from RR BLOWER 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 from RR HVAC fuse 24 through CKT 341 (BRN) to the coils of the three auxiliary blower motor relays. This voltage is available when the ignition switch is the RUN position. This voltage operates the relays. The auxiliary blower motor switch grounds the coil of the selected relay through CKT 15 (BLK) through ground G400. When the relay coil grounds through the auxiliary blower motor switch, the current flows through the relay coil in order to close the relay's normally-open contacts. Voltage is available to the relay contacts at all times through CKT 1542 (RED) from the HVAC MaxiFuse®. When the relay contacts close, this voltage operates the motor.

Placing the auxiliary blower motor switch in the LOW position grounds the coil of the auxiliary blower motor low speed relay through the wire for CKT 1926 (DK BLU) and CKT 60 (YEL). The relay's contacts close and apply operating voltage in CKT 1176 (YEL). The current flows through both the resistors in the auxiliary blower motor resistor and through CKT 1172 (YEL) to the auxiliary blower motor. The voltage drop through the two resistors limits the auxiliary blower motor to the lowest speed.

Placing the auxiliary blower motor switch in the medium position grounds the coil of the auxiliary blower motor medium speed relay through wire for CKT 1925 (RED) and CKT 63 (TAN). The relay's contacts close and apply operating voltage in CKT 1072 (LT BLU). The current flows through only one resistor in the auxiliary blower motor resistor and through CKT 1172 (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.

Placing the auxiliary blower motor switch in the HIGH position grounds the coil of the auxiliary blower motor high speed relay through wire for CKT 1924 (WHT) and CKT 52 (ORN). The relay's contacts close and apply operating voltage directly in CKT 1172 (YEL) . The current flow bypasses the resistors in the auxiliary blower motor resistor. The full battery voltage allows a high speed of operation for the auxiliary blower motor.