Trucks a tool

On my Chevy Colorado truck, the Heater/AC fan switch has 1 2 3 4 speeds and it used to work on all 4. However it now works ONLY on 4. It must be getting input power and is obviously connected to the fan so my guess is the switch is bad NOT a connection to it??? New switch needed or a connection problem???

Experiences and Opinions appreciated, then figure out how to remove it grrrrrrrrrrrr

John T

Blower Motor Control Module / Resistor down on the heater box about $25 or less. There are u tube videos that show how to change it.

http://www.1aauto.com/videos
http://www.1aauto.com/videos

Hey John T - 99% chance the blower resistor has burned out.

The resistor is wired in series with the blower motor. The blower switch selects taps on the resistor for the the 3 slower blower speeds. However on high speed the switch bypasses the resistor so the motor sees full system voltage. Thus a bad resistor gives only "off" and maximum speed.

Trick now is to find the resistor (I'm not familiary with the Colorado). The last couple I've replaced (80's era Chrysler and GM) had the resistor in the heater cold air plenum with the terminals on the firewall - relatively straightforward to replace.


...Bob M

Oh boy john I get to help ya with an electrical problem. Gm had a tsb. Tec service bulletin on a lot of the pickups. The pigtail harness going to the blower motor overheats and gets a little meaty. They have an update kit that comes with a new pigtail and the resistor block. All located passenger side behind the glove box.

JohnT,
It could be the fan, it could be the resistor, and there may be a thermal fuse in series with resistors.

It's easier to replace switch first.

If I recall, the switch shorts out part of the resistor, lowering resistance, current increases and fan runs faster. On HI, no resistance is used. Switch applies full power to motor.

Because switch is easier to get to, start there. Could be the connectors at switch are burnt off.

Have fun getting to the switch and or resistor.
George

I had the same problem with my 03 Chevy p/u. Replaced the resister. Easy fix. The problem I have now is on a Saturn car that did the same as your truck, but the fan stopped altogether. I could not drive the car last winter as I had no heat or defrost. I have tried to take apart the dash, but have not finished the task. Now this summer it started to work like it should. Grrr!

That's typical resistor failure. They burn out.

On my Silverado it was no big deal to change. The resistor is on the bottom of the air plenum on the passenger side. One plug, two screws, 10 minutes including finding the right wrench.

It was the resistor on my car John. The resistor lives in the air duct on some models. Before the age of computers, the resistor was shunted for high speed, and that's why the blower would fail on the low speeds only, but still work on high. It was pretty easy to change on my '03 Impala, but I'd also check out Glennster's tip.

You win Ten Silver Dollars, look for them the second Tuesday of next week lol See my PS above.

John T

I had an old Chevy that did that and was told the motor was shot and would only work when the larger amt. of juice from the high position was sent to it. The lower speeds didn"t afford it with enuf poop to spin the dud motor.

Its working for now at least with a "temporary" (sometimes those end up permanent) band aid cure:

Okay THANKS TO ALL, you gave me a start in the right direction (all I needed for me to run with it) after which You Tube and the parts house Dave mentioned finished it up (pictures help you find the resistor etc).


It was NOT so much the resistor block itself (but connection to its 4 male pins), it was (like Glenster mentioned) the 4 pin female electrical cable connector that goes to the resistor that failed. The You Tube Video showed exactly the same problem, the 2 center pins on the connector were burned and carboned. Using a knife and o ring puncture wound tools I was able to de carbon and bend and tighten the connectors female end so it fits tighter onto the resistors male pins, and I works for now at least on all 4 speeds.

The parts house Dave mentioned has great pictures of resistor blocks and connector pigtails which I have saved and will order as needed.

It was surprising how easy it was to get to, sort of up under behind the glove box in plain sight yayyyyyyyyyyyyyyyy The You Tube video you mentioned was so helpful

THANKS YALL, I'm a happy camper for now and if and when it fails a new resistor or perhaps just a new pigtail connector (that's where damage was) will fix it more permanent I'm sure.

Im about as bad on my truck as my RV, but on it Im SUPER SENSITIVE. I have to have absolutely everything on it perfect or I loose sleep and work until its perfect grrrrrrrrrrr. But if youre in the Middle of Nevada or Utah up in the mountains 100 miles from any towns or repair shops or even cell service, that's just the way I want to be plus having a ton of tools and some critical spare parts etc etc. Still, even on a new RV Murphys Law kicks in and things go wrong but the more prepared the better I say.

John T Now that fun is over I have a couple law jobs to get at, make gas money for the RV lol

Thanks for the kind words john!!! Get the gm replacement pigtail, it cures the problem. The original pigtail was not heavy duty enough to handle the current draw. We replace quite a few here at the shop. Solder and heat shrink the connection, instead of using the butt connectors that come with the kit.