chainzaw

I disconnected the wire connectors at the motor. Put volt meter on the wires. I only get 12VDC when the dial is on high. 0VDC on any other setting. I pulled the dash apart and looked at the speed dial. It looks more like a switch with several wires coming off of it than a motor controller. Does anybody have a wiring diagram they can post? Any ideas? I tried the search with no luck.

biododge1

That is a classic sign of bad fan resistor pack

nickg

blower resistor is more than likely shot, heater switch controls the GROUND side of the fan motor (at least according to my repair manual)

blower resistor is located down near fan motor, unplug connector then remove resistor block, windings/coils can be checked with a multi meter, (should have no opens) have heard reports of guys soldering broken wire and having it work, another thing to note, sometime a failing (high amp draw)fan motor can burnout the blower resistor.

old 300

As stated by nickg and biododge1 its usually the resistor. Mine went out in August but I only lost low speed. They tell me that is very rare, usually you only have high speed. I my case when I removed the resistor it was cracked and looked like it was wet because it was rusty and turning green.

chainzaw

thanks for the advice. i'll take a look tomorrow

johnh

be forewarned... the biggest cause of resistor failure is the bearings in the motor are going out....i replaced two resistors before i replaced the motor... the bearings bind up and cause the motor to not rotate as it should, in turn causing the resistor to over heat and burn out

chainzaw

How noticeable is it if the motor bearings are shot? If I drop the fan down out of the housing do you think I can tell if it needs to be replaced or not?

johnh

i could tell on mine, didn't spin easy