sounds like its dealership time..I imagine the control head haS GONE NUTS,a sensor has,or the aspirator in the headliner...

 

well, thanks for the help.

 

sorry i'm not more help..but its gonna have to be checked for codes...and only a dealer scanner will talk to the hvac head

 

I take it they'll charge me to plug it in and run the codes?

 

oh ya...but shouldn'tbe too much...

let me tell ya,those auto hvacs are tricky to diagnose

 

That's why I'm hesitant to go out and by a new head. I just don't want to get into replacing something to find out it something else.

 

I hear ya....take it from me..these things are tuff..

I've seen heads,temp sensors in the vents,temp sensors up front,the aspirator by your head,connections,actuators,you name it....a lot to go wrong there

 

That odd, a gm guy, and I know you're one, but a guy at the dealer told me there was only one temp sensor in the whole truck. I told him he had to be crazy, that just didn't make sense. So there are more? How many and where? And what's the aspirator?

 

the aspirator is that little grille by your head..its a small fan that sucks in air to measure the cab temp...

there is a temp sensor in each duct left and right,so the head knows how hot/cold the air is that its putting out.
then the outside sensor by the radiator...
then rear temp sensors if its a 4-door or utility

if ANY of those skew,its going nuts

 

So if it turns out to be something like one of the little items, can the gm code readers tell which one it is?