2004 Denali Climate control is only hot or cold

[Xing_Gateway]

Ok so my Yukon Denali climate system is strange. If I use the temp knob to adjust the temperature it actually fights me... I'll turn it up and it will go up and then back down a couple of degrees.

Ok strange. The strangest part is it only seems to have 2 temperatures. Anything 89 degrees and under it blows cold, same temp doesn't get any colder. When I get to 90 and above then it gets hot, and same temp doesn't get any hotter above that.

So basically I can't control it too well.

I've done the remove fuse to reset thing and didn't help.

Any ideas?

 

[Big Mama]

Welcome to the forum from Virginia. That’s a strange one but someone better versed than me will chime in soon.

 

[strutaeng]

I've got the same symptoms on my 06 Suburban... subscribed for the content

I "think" it's the module, but don't really know how to test it.

Further, on mine when I start the truck in the morning when it's cold, turning the temperature wheel clockwise actually turns the temperature DOWN! It's freaking aggravating because I'm usually trying to turn the temperature up to defrost dew on the windshield. After it warms up it works fine. I took the AC module apart (to do the led upgrade), sprayed the knob thingy with deoxit and it seemed like it worked fine for a few days. That's why I'm thinking it's the actual ac control module...

 

[Donal]

Ok so my Yukon Denali climate system is strange. If I use the temp knob to adjust the temperature it actually fights me... I'll turn it up and it will go up and then back down a couple of degrees.

Ok strange. The strangest part is it only seems to have 2 temperatures. Anything 89 degrees and under it blows cold, same temp doesn't get any colder. When I get to 90 and above then it gets hot, and same temp doesn't get any hotter above that.

So basically I can't control it too well.

I've done the remove fuse to reset thing and didn't help.

Any ideas?

I encountered a 05 Suburban several years ago with those conditions and discovered the aspirator above the driver position was not functioning. Actually the wires had been clipped by someone. Two butt splices restored Hvac operation.

 

[Meathead16]

x2 on that temp sensor above the drivers head. When the system is set to 60° it operates for max cooling and at 90° max heat, regardless of any other input. Not sure what the default that the computer uses when sensor signal is lost but it's neither here nor there, just needs replaced. The temp selection knobs doing their own thing is maddening beyond anything I've ever experienced. It's an issue with the module itself 7and the encoder motors that control the temperature. I've found that if you push on the middle of the knob with decent pressure, and simultaneously turn the knob very slowly, about 1 incremement per second, the temp will cooperate. Turn it any faster though and you're back to square one.

 

[Fless]

You can use some canned air to clean out the aspirator. Worth a try.

 

[strutaeng]

You can use some canned air to clean out the aspirator. Worth a try.

Actually, I spoke too soon. Truck is back to doing the same thing. Doh!

I ordered a new temperature sensor...

 

[strutaeng]

x2 on that temp sensor above the drivers head. When the system is set to 60° it operates for max cooling and at 90° max heat, regardless of any other input. Not sure what the default that the computer uses when sensor signal is lost but it's neither here nor there, just needs replaced. The temp selection knobs doing their own thing is maddening beyond anything I've ever experienced. It's an issue with the module itself 7and the encoder motors that control the temperature. I've found that if you push on the middle of the knob with decent pressure, and simultaneously turn the knob very slowly, about 1 incremement per second, the temp will cooperate. Turn it any faster though and you're back to square one.

Yes, I've noticed that too on the knob. Applying a bit if downward pressure while rotating the knob works...and turn it slowly.

 

[Fless]

Yes, I've noticed that too on the knob. Applying a bit if downward pressure while rotating the knob works...and turn it slowly.

While you're waiting for your new aspirator grab a can of air and blow out the one that's in there now. Might make a difference before you change it out.

The HVAC heads aren't difficult to remove and disassemble; consider doing that to clean the internal contacts with some Deoxit D5 or something similar.

EDIT: here's what they look like inside. I had mine apart to clean the two pots and to replace the bulbs.

 

[strutaeng]

Actually, I spoke too soon. Truck is back to doing the same thing. Doh!

I ordered a new temperature sensor...

Ok, I just installed the new sensor. It's fixed!!!

I did add a bit of hot melt glue because it wanted to get push out to one side such that the fan was not on the hole.

I wedged some boards in there to get the harness unplugged, but still a little tight. I took apart the old one and the wheel didn't spin freely, even after adding a drop of lubricant. The wheel just slides out.