Variable fan speeds not working

[CAMAN]

My 05 Chevy Colorado just recently started having problems with the HVAC blower. The fan speed switch works intermittently. Sometimes it works fine then it will cutout and only work on high. I can flip the switch back and forth a few times and it will run fine for a bit then cutout again.

Does this sound like the switch is bad or is there a relay or resistor somewhere else that has gone bad? And if it's a relay or resistor where would it be located?

[tweedlap]

Somewhere on here I saw box fan for sale. Maybe you could get that.

tweed

[ratherbefishin]

I have seen resistors go bad on the newer chev 1/2 ton trucks, aslo on my 04 3/4ton. On these trucks they are located under the glove box and you have to remove the hush panel to get to it. Not sure on the colorado

[katophil]

+1 on the box fan!!!

[Jeremy airjer W]

Without having a wiring diagram in front of me I would be hesitant to fire a resistor at it. The resistors either work or they don't work. There is no in between. I'm not exactly sure what they use to control fan speed but I will check tomorrow unless somebody else does before that.

[CAMAN]

Alright, thanks. I've heard this is something fairly common in GM's around this age, but never heard the exact fix, and if its something I can do on my own.

[Scott K]

These had problems with the blower motor drawing to many amps and burning out the resistor.

But I agree with airjer, when it goes bad, it is bad. I would check the ground wire for the resistor. If you need to just tap a new ground wire into the existing one and see if the problem reoccurs. It is pretty much a free fix if that is it.

[CAMAN]

4Wanderingeyes, is the resistor still located behind the glove box?

[Scott K]

4Wanderingeyes, is the resistor still located behind the glove box?

Yep, just to the left of the blower motor.

[CAMAN]

Ok, thank you. I will check it out.

[Shack]

Quote:

The resistors either work or they don't work. There is no in between.

This is true. Same as a light bulb, or is it "really" the same. Could the resistor be broken but touching on occasion and then not? Like broken filament in a incandescent light bulb touching and then not when moved? The ones I have seen that burn out melt away a good distance and will never touch. If it is cracked I could see this happening.

Could be the connector at the resistor? Could be melted or burnt. I would rule out the blower motor if it is working on the high (12v) setting all the time?

[CAMAN]

I started diging into it the other day and started following the wires to see if I could find the resistor. As I approached what looks like the main power cord (4 large wires) for the fan it started going haywire as I jiggled the plug. Unplugged it and saw a little white corrosion on one of the contacts. Cleaned it up as best I could and its been working flawless since. I'll be getting a little dielectric grease to throw in there, but hopefully that was the only problem.

Thanks for all the input guys!!