2004 Chev with touchy heat control

[ZapMan]

I have a 2004, 2500 silverado 4dr with a 6.0

The probem I have is a touchy heat control. On long trips it seems I can't get that warm just right temperature. I only get hot, and if I adjust it down a bit it turns cold. I push it back up just a touch and in a few seconds it hot again. I run this vicious cycle nonstop on long trips. Up-down. What is causing this?

[huntingislife]

Mine does the same thing. The sweet spot is about 2/3 towards the cold side. One notch to the left and its cold. One notch to the right and its hot. It does get annoying some times.

[Scott K]

I have ran into a few concerns where a harness gets pinched behind the glove box. Open the glove box, tip it down all the way, there is a harness on the left side of the opening, inspect the harness, to see if it has been getting squished. If so repair the harness, if you dont see anything, before closing the glove box, try the heater, see if it works better, wiggle the harness, see if the temp changes, if so, it is in the harness there. If not, you may want to bring it in to see if there are any HVAC codes.