Blower Motor erratic

[richgod]

Well... yesterday my blower motor wouldn't work at all on my '93 D250. . Power seemed to be getting past the switch (new switch), but no air was getting moved. Today, when I cranked the beast, blower came on full bore (Switch was in the high setting, and control was on 'heat'). Blower works at all settings now. This happened about 2 months ago, and I replaced the motor switch.

I was preparing to remove everything and replace heater core/blower motor. But now I'm wondering if that is what needs to be done.

This morning it was cool... aroiund 33 degrees, when I started the truck, but I don't see how that would affect it.

Recent repairs (3 weeks ago) have been lift pump replacement and injection pump rebuild, and parking brake bracket adjustment.

Does anyone have suggestions as to WHAT might cause erratic function like this?

 

[B.G. Smith]

All the power for different speeds for fan come through a resistor bank except high which is direct. If it falters again, turn the switch to high, if fan comes on then the resistor is more than likely the problem. Resistor is located in bottom of AC/Heater housing under the glove box. bg

 

[richgod]

Thanks BG... another dumb question, since i have never been in that area of the truck... If I have to check it out, Is the resistor accessible without removing the AC/Heater housing and draining the AC system/heater lines??

Can't find that infor in the shop manual...

 

[B.G. Smith]

Yes it is accesable without any teardown, it is held in place by two small screws. Remove the screws and it un-plugs from a receptacle. I can'tell tyou the sequence to check the terminals, the one in my truck is encased in ceramic. If it is good there should be continuity reading between any two terminals I think. The resistance would be different for each speed. On mine the terminals where it plugs in were corroded and I didn't notice it when I replaced it, a few months later it quit on low speed again and then I found the corrosion, cleaned everything up and put the original resistor back and it's working fine ever since. bg