Hvac Gone Nuts

pwall · November 9, 2007

Today, the hvac system in my 2002 YukonXL went nuts. The fan will run at top speed, regardless of the temperature settings and regardless if the fan is on or off. Rear defroster also no longer works.

Really weird thing is when I turn of the truck and remove the key, the fan keeps going. There is no way to control it.

Ended up pulling the 25amp fuse from underneath the front hood to shut it down.

Rear hvac seems to be running as normal.

Here is a picture of the hvac I have (the numbers are in celcius.....):

Any help you can provide would be greatly appreciated.

pwall · November 10, 2007

bump

pwall · November 12, 2007

Brought it into the dealership this afternoon...hopefully it won't cost too much.

alz · November 13, 2007

A friend had the same problem with his Grand Prix. There was a leak in the front cowl down in front of the windsheild. It would leak onto the blower motor I believe and shorted it out. The dealer had to fix this twice before it was resolved.

20jake20 · May 18, 2008

What turned out to be the problem?

Today, the hvac system in my 2002 YukonXL went nuts. The fan will run at top speed, regardless of the temperature settings and regardless if the fan is on or off. Rear defroster also no longer works.
Really weird thing is when I turn of the truck and remove the key, the fan keeps going. There is no way to control it.

Ended up pulling the 25amp fuse from underneath the front hood to shut it down.

Rear hvac seems to be running as normal.

Here is a picture of the hvac I have (the numbers are in celcius.....):

Any help you can provide would be greatly appreciated.

C6Racer · May 20, 2008

I have a similar HVAC control setup except that I don't have the rear defrost buttom or the numbers on the temp control. One day I was driving my truck and the lights from all three buttons on the bottom came on for no apparent reason. I didn't see or hear anything weird nor would the blower motor come on if I turned on the blower speed switch. Happened several weeks ago but, hasn't repeated it since I turned off my truck that day after it had happened. Any ideas? Thanks