Hey all...my 2000 SSEi HVAC system seems to want to decide what climate I enjoy. Fan on full blast, AC in the winter...it even seems to think it knows when the rear window needs defrosting. When this happens, no physical commands are accepted...it just continues doing what it likes. After a few minutes, the 3 dashes show up. Often if I shut off the car and restart, the problem is gone.

Is there any way to disable this automatic control system via bypass of some sensor, and if so, where is this sensor? Does anyone know what my problem is and where to look? I searched and came up empty both here and all over the internet.

Thanks guys...

It definitely sounds like you have a defective controller, that will need to be replaced but before we go there have you tried to retrieve any codes from the system. Also if you have access check TSBs on this problem

My last reply didn't post for some reason.
I looked at TSBs in Mitchell On demand didn't really come up with anything. How does the system work manually?

You need to purchase a new (or used) HVAC control head.

00 05 Pontiac Bonneville Heater Controls AC Digital Dual Climate | eBay

Replaced control head, no change. The system works perfectly in manual without any problems...until it takes over in auto.

No other ideas...?

Are you sure the control head you installed is a good one. Was it used?

Yes, used. Tested in another bonneville, works fine. Moved that control to my car and it does same. It is something in the car...

Now it doesn't seem to do it over the last few days. Intermittent is scary.

Anyone have a wiring diagram for this thing?