Problem With Heater Controls

98silvz71 · February 23, 2009

I am having some problems with my heat in the truck. I got in this morning and the heat was stuck on. I could control what vents it went to and the fan speed but not the temp. It kept blowing hot air even if the a/c was on. And the a/c was working, I knew it was on and it was pumping cold out the top of the compressor. Can anyone shed some light on this for me? Is the heater control box bad in the dash?

eaton3122 · February 25, 2009

Mine has done this same thing a few times as well. Seems to always correct itself if I turn the truck off then crank it back up. I've searched a little bit here on the forums about this and it seems like it may be the blend actuator door getting stuck in one position. I have not pursued fixing mine any further, but if it starts to do it more often, I will have to. Maybe someone else can shed some more light on this topic for you too.

390pi · February 25, 2009

I have the same problem in my 2000 Suburban. I seem to remember reading something about shimming the blend door somehow.

Now, I can't remember where I read that.

390pi · February 26, 2009

There was this thread about replacing the actuator:

http://www.gm-trucks.com/forums/index.php?...=heater+problem

wgabert · February 26, 2009

I am having some problems with my heat in the truck. I got in this morning and the heat was stuck on. I could control what vents it went to and the fan speed but not the temp. It kept blowing hot air even if the a/c was on. And the a/c was working, I knew it was on and it was pumping cold out the top of the compressor. Can anyone shed some light on this for me? Is the heater control box bad in the dash?

I posted this awhile back. Hope this helps.

I found on my 02 that the heater would stay in HOT quite often. I removed the blend door actuator and plugged it back in to the harness to see if it would cycle. Seemed to work OK. When I re-installed it I noticed that the act pushed up on the blend door maybe 1/4 in or so and then would not work smoothly. It appeared to me that the door being pushed up made it bind, probably up top. there are three mount holes in the act. One is a locating pin. I installed two small washers on each of the remaining mounts in between the heater box and the act so it brought the door down a bit. Been working now for over two years without a hitch. If you install a new act I would still add the washers.

390pi · February 27, 2009

I found on my 02 that the heater would stay in HOT quite often. I removed the blend door actuator and plugged it back in to the harness to see if it would cycle. Seemed to work OK. When I re-installed it I noticed that the act pushed up on the blend door maybe 1/4 in or so and then would not work smoothly. It appeared to me that the door being pushed up made it bind, probably up top. there are three mount holes in the act. One is a locating pin. I installed two small washers on each of the remaining mounts in between the heater box and the act so it brought the door down a bit. Been working now for over two years without a hitch. If you install a new act I would still add the washers.

Yes, that was the fix I had read before. Thank you!

It seems after reading though several other old posts about this same issue, the dealers keep changing out the actuators but that never solves the problem.

98silvz71 · February 27, 2009

Thanks for the info. I will look into seeing what I can do to fix it. Most of the time I keep it all the way on cool so I don't normally have a problem. But lately I have been leaving the truck at home and driving the HHR instead.