HVAC control ssues on 07 classic

[stoltz23]

at about 30K my hvac started doing weird things. It no longer shuts off. i can turn the first knob to off and air still comes through the vents whatever position i have it set on. It was ok in the summer cause i woudl just put it to the floor and put it on cold. now tha ti need to turn the heat on it is annoying because i am constantly changing the temp cause either my feet are sweating or cold. anyone else had this issue? also are the digital style control interchangable with the manual one liek i have?

[Black06]

try turning the recirculation button off......

[DarkSilvr]

switch it to the windsheild

[ibthumpin]

Unless GM's HVAC system has changed in the last couple of years, turning the blower "off" wont keep fresh air from entering the cabin through the vents - if the fresh air button is active.

To stop incoming air, you've got to turn on the recirc feature - this closes off the incoming air and will recirc the cabin air (providing the blower is set to someting other than off). The A/c compessor will also cycle on and off when recirc is active.

[stoltz23]

i never turn that button on will have to see if that does anything

[stoltz23]

would like to bring this thread back because over the weekend my lights went on part of my hvac unit. i have the manual one wiht the two knobs but would like to replace it with the digital one that dives you the temp since i have to replace it now anyway. are these interchangable? does anyone know

[east302]

I've seen a lot of people asking that question, but only saw one "answer" to it. The quick answer is Yes, it can be done. As you can guess, there's a "but..." after that.

Here's a link that kind of goes over the process.

http://montecarlo.homedns.org:8080/wiki/index.php?title=Silverado_Auto_HVAC

Here's another link with a discussion on the above:

http://www.silveradoss.com/forums/index.php?showtopic=34912&st=0

I don't think the guy was finished writing about the swap, but you might be able to contact him for follow-up information.

[StumpyandhisZ71]

I am having a similar problem in my 04 GMC with the same type of controller. My problem is slightly different in that I cannot get it to change from the window defrost position. No matter what is switch the direction knob to, it is always on the window defrost. My toes are cold whats the issue here?

[stoltz23]

sounds like just the control unit has some bad electronics. go to the dealership and ask for a wiring diagram for your system. and make sure there are not any other electronics other than the master control unit that change the location of where its blowing. To my knowledge there is nothing else. so you should just have to replace your control unit thas in the dash. but i coudl be wrong