Blower Motor Resistor: Description and Operation

SYSTEM OPERATION
Front
The front blower motor resistor is mounted to the inboard side of the heater-A/C housing in the engine compartment. It can be accessed for service from the engine compartment. It is secured to the housing with two screws and is connected to the headlamp and dash wire harness. See Blower Motor Resistor - Front in the Removal and Installation for more information.

The blower motor resistor has multiple resistor wires, each of which will change the resistance in the blower motor ground path to change the blower motor speed. The blower motor switch directs the ground path through the correct resistor wire to obtain the selected blower motor speed.

With the blower motor switch in the lowest speed position the ground path for the motor is applied through all of the resistor wires. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed. When the blower motor switch is in the highest speed position, the blower motor resistor is bypassed and the blower motor receives a direct path to ground through the high speed blower motor relay.

The front blower motor resistor cannot be repaired and, if faulty or damaged, it must be replaced.

Rear
The optional rear heater-A/C unit has a blower motor resistor mounted to the inside of the unit lower housing in the passenger compartment. It can be accessed for service through the horizontal duct opening in the rear heater-A/C unit upper housing. It is secured to the inside of the lower housing by two mounting tabs and a snap feature that are molded into the lower housing, and it is connected to the rear heater-A/C unit wire harness. See Blower Motor Resistor - Rear in the Removal and Installation for more information.

The blower motor resistor has multiple resistor wires, each of which will change the resistance in the blower motor ground path to change the blower motor speed. The blower motor switch directs the ground path through the correct resistor wire to obtain the selected blower motor speed.

With the blower motor switch in the lowest speed position the ground path for the motor is applied through all of the resistor wires. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed. When the blower motor switch is in the highest speed position, the blower motor resistor is bypassed and the blower motor receives a direct path to ground through the high speed blower motor relay

The rear blower motor resistor cannot be repaired and, if faulty or damaged, it must be replaced.