1999 Chevy Heat/AC Control Problems

[MacGyver]

I'm having intermittent issues with the heat and A/C controller in my 1999 Silverado:


Lights for recirculating and fresh air are both out (one or the other should be on)
A/C light stays on and I can't turn it off
Rear defrost button doesn't do anything
Defrost/dash/floor selector doesn't do anything
Temp selector doesn't do anything, all I get is cold air
The fan speed control DOES work though

Sometimes it works normal, sometimes not. Any ideas?? It's still winter here and I need my heat and defrost!!

[old377guy]

I'm no GM tech but if it's ECM controlled, you might try disconnecting battery to re-boot system?- Good luck.

[ROGUE]

This may not be related but I had a very strange problem on a 02 Monti Carlo that sounds similar. In this case it also involved the cruise control as well as the climate control group. Without writing a book about the troubleshooting involved, it ended up being the ignition switch. A power lead from the ignition was suffering a voltage drop that was affecting those circuits. I think if I remember right it was a yellow wire with a black stripe maybe. Replacing the ignition switch solved the problem. Good luck, I consider myself a pretty good electrical troubleshooter and this one had me going for a while. A hint from a GM engineer on a GM site set me in the right direction.

[HiZ]

Remeber when it was 50 last week?
Hey how about you try to remove the module for your Climate control
I'm not sure on the specific year but they were updated to BCM control
However when BCM issues come to be it is usually not just climate control
So, I would have to say your module would be the key, that's the controller that has the display, knobs, etc on it > I would start there