Blower Motor Resistor: Description and Operation

HEATER BLOWER MOTOR SWITCH RESISTOR

Blower Motor Resistor:

The heater blower motor switch resistor assembly operates in the following manner:
^ The assembly is located on the passenger side of the A/C evaporator housing behind the glove compartment.
^ Three resistance elements are mounted on the resistor board to provide four A/C blower motor speeds.
^ Depending on the blower switch position, series resistance is added or bypassed in the A/C blower motor circuit to decrease or increase A/C blower motor speed.

The heater blower motor switch resistor assembly, which is similar to a standard resistor assembly, operates as follows:
^ An overheating protective device (thermal limiter) has been added to prevent heat damage to the A/C evaporator housing.
^ Overheating of the resister coil(s) will occur when system airflow is stopped by excessive heat; replace only with identical replacement.
^ Do not substitute heater blower motor switch resistor with a standard assembly which does not include a thermal limiter device.

HEATER BLOWER MOTOR THERMAL LIMITER

Blower Motor Thermal Limiter Resistor Assembly:

The thermal limiter, used in the heater blower motor switch resistor, performs the following functions:
^ Serves as a temperature protecting fuse.
^ Is located a predetermined distance from the resistor coils and in series with the coil circuit.
^ Will open the resistor coil circuit when the temperature of the thermal limiter circuit reaches 121° C (250° F).

NOTE: Replace the entire heater blower motor switch resistor assembly because the spring contacts cannot be closed again.