Blower motor reistor on 2001 Pontiac Sunfire

#1

All of a sudden, within 6 months, I have blown 3 blower motor resistors. Does anyone have any ideas whats going on?

#2

The blower motor, itself, is drawing too much current, and may, sometimes, exceed the fuse amperage rating. You could put an amp meter on the blower motor circuit, and measure the amperage draw for the different speeds. Be sure that the test ammeter is rated higher than the blower fuse.

#3

Although The Blower Motor Works, It Is Probably Bad Or Restricted, Drawing Too Much Juice.

#4

So shouldn’t the 25 cent fuse be blowing instead of the $25 resistor?

#5

Not really, because the resistor has been going through many cycles of heating and cooling. The resistor coil gets near red hot and eventually the repeated heating/cooling cycles fatigues the metal and it snaps.
This occurs without exceeding the rated load of the fuse.

#6

The resistors are cooled by the air that the blower blows. It’s no longer blowing enough air (for the amount of power it is taking) to keep the resistor cool enough. The fuse is only there to protect the wiring and prevent a fire. It has to be able to handle the max current required at the max speed setting. The lower speeds are less current.

#7

The fuse has to handle the surge of current that comes with the motor stopped just as the switch is turned on. That could be 30 amps while the motor running at full speed might draw 15. If the blower motor bearings are shot, it could be chronically drawing 20 or 25 amps and that might heat up the control resistor too much.

Are you sure it is the resistor itself burning out and not the connector? That can happen as well. Look at or test the resistor coils themselves. You should see only a few ohms with a VOM.