Thread: Issue with climate control mode

Took the Grand Prix out of winter storage this past week & so far so good, but I did run into a little hiccup with the climate control system. I have the basic single zone 3-knob setup. What happened is its stuck on the bi-level setting (blowing from dash & floor) which is where it was when I put it away for the winter. There is no vacuum tension trying to change modes. It just turns without feeling much if any resistance, but doesn't feel like the plastic knob itself broken (went through a lot of those years ago with my old grand am). I also thought it would default to defrost mode if there was a vacuum problem. Is there anything common that would cause this to happen before I start tearing everything apart?

Dumb question but did you pull the knob and use one of the other ones to try and turn it? I've noticed that 3-zone control on mine would get harder to turn when it sat and ended up with a cracked knob that would move but not turn the metal post in the HVAC unit all the way.

Pull the knob and see if you can move the post with pliers and get it to change direction. If that doesn't work then I'd think either a line is messed up or the HVAC unit is leaking vac.

IMHO if it doesn't default to defrost then I wouldn't think it's a vac problem as IIRC a loss of vacuum would indeed put it on defrost.

I got my answer. I pulled the knob and you are correct, it was cracked. Not big enough to fall off on its own, but small enough to still hold the metal ring and flex when I turned it instead of turning the stalk on the switch. I'll try that dorman kit that has the three different ones first...its cheap enough. I guess I was dumb enough not to think of that in the first place lol

Glad you found it! Not dumb, I've jumped to conclusions before and have been bit with the simple answer. 20 yr old plastic knobs aren't what they used to be, lol..

No these 20+ year old knobs aren't lol. I guess I was assuming it would have just fallen off into my hand. That dorman kit worked... it has 3 different knobs, but the one matched up & did the trick