So here is the deal. The HVAC control on my 97 C5 crapped out on me a few weeks ago. It had been rebuilt a few years back, so I figured I'd buy another one, so I would just be able to swap them out in the future. What had happened was it would not come on in the colder mornings, but would sometimes come on with the vehicle on run (engine off), but as soon as I turned it over, everything was blank. Additionally it came on in the afternoons when it was warm. I put in the new controler last week, and everything was perfect. I washed my car last night, and did a few other things, and still perrfect. This morning I go to leave for work (of course I happened to be running a few minutes late) and nothing. So my windshield fogged up, and no way to clear it. I figure it has to be electrical, and I have no idea where to start. So any help will be appreciated. I've had a few other problems that need fixing in the next few months, but I don't want to mess with all that if I can't drive the damn car. So I'm sorry for the long rant, but I'm so frustrated with the whole thing, and I've decided that if I can't fix this by next week or so, I'm selling the thing. Yeah, that upset. So thank you in advance for everything you guys come up with. I figure someone on here has to have the answer. This forum hasn't let me down yet.

Update: The HVAC controler comes on and off now, intermittently, and I have no idea why. I have not done anything different. Sometimes it is on when I start the car, most times not. It came on about three quarters of the way home as well. Any suggestions? I'm pulling my hair out here!!!

 

Anyone?

 

Does that mean it's completely dead, or just no display? can you turn on the a/c, switch modes, etc?

 

If the screen is off (Always in the mornings and unless it is hot outside) it is dead. No nothing. When the screen decides to work, everything is perfect.

 

If I understand correctly, you have installed a "new" control head...meaning not used..

If that's the case, then you'll have to evaluate the 12 volt input and ground with a meter to see what's dropping out.

 

I believe I have just gone crosseyed looking at the diagram...I'm so confused...so I need to buy a volt meter and start testing the wires? How do I go about doing this? And no, it was a used unit, but I find it hard to believe that both would have the same problem. I figure it has to be something in the wiring. Hopefully I can figue this all out....I don't really understand electrical....wish me luck!

 

Or take it to a shop and have them troubleshoot it for you.

Plenty of us can walk you through it, but it might be difficult for you if electrical troubleshooting is not your thing.

 

Well I'd like to try to do it myself, because a: I don't like paying an arm and a leg to have things done that I should be able to do myself, and b: how else will I ever learn if I don't do it? I'm a hands on guy. So I believe with some guidence I should be able to do it. Where do we start?

 

You will need a meter. It does not have to be anything high end, just capable of measuring resistance and voltage.

 

Ok, I will pick one up tomorrow.