Blower Motor Resistor
Auxiliary Heater & AC
LevelWarrantyStandardBlower Motor Resistor Replace
My information does not list a separate fan switch for this model; it may be part of a control assembly which would explain the high cost.
Blower Motor Speed Control
The blower motor is controlled by a four-position heater blower motor switch located on the left side of the control assembly. The four positions are LOW, MEDIUM LOW, MEDIUM HIGH and HIGH. The four operating speeds are obtained with a heater blower motor switch resistor connected in series with the heater blower motor switch operating on the ground side of the blower motor.
With the function control knob in the OFF position, the blower motor will not operate.
With the heater blower motor switch at LOW, current flow in the ground circuit is through three resistors to obtain the lowest operating speed.
With the heater blower motor switch at MEDIUM LOW, current flow in the ground circuit is through two resistors to obtain a medium low operating speed.
With the heater blower motor switch at MEDIUM HIGH, current flow in the ground circuit is through one resistor to obtain a medium high operating speed.
The way it all works is as follows:
Power is supplied to the blower motor from the blower motor relay on the pink/white wire. This part of teh circuit is OK, if it works on high speed.
The ground is switched through various resistor combinations to control low speeds.
the black wirte from teh AC control assembly is the ground source for teh circuit. The AC control connects this ground to teh blower switch through the red/ orange wire to the blower switch. The blower switch then connects the ground circuit to the lg/w, y/rd wires to pass through one or 2 resistors dependinon speed selected. The orange/blk wire from the switch to the resistor bypasses the resistors and dirrectly grounds the circuit for high speed operation. There is a thermal limiter (fuse) built into the resistor block itself.
On medium speeds with everythign conencted, check for power at teh y/rd or lg/w wires at the resistor; if there is no power present there, then the resistor is probably open and likely the source of teh problem. Resistors fail much more often thatn control switches due to heat, moisture, and vibration present in the heater case.