AC Control Panel smoked...

[doncaruana]

I have the original AC control panel and 285,000 miles on my '97 Tahoe. Last night while driving I started smelling something burning. There was smoke coming out of the CD slot (that mounts right below the AC control panel). I shut everything off and the rest of the stuff seems to work except the rear window defroster button no longer lights up.

I've not really had any issues, per se, with the only thing I would mention is that my blower is always blowing at least a little air (just slightly less than on low), even when it's off.

Before I rip open the dashboard, does this sound like it's just the AC control panel and a replacement of that would be fine? Or is it more likely the problem is deeper and as soon as a put a new panel in, it fries as well? Or for that matter, is it likely that the defroster circuit itself is fried also?

I can get an AC control panel with +200K miles on it from a local junkyard for $50. Should I just go for that and see what happens?

 

[drakon543]

it could be a number of things so yes you could fry the next one also. are you sure the blower motor is always on or is the vent door not closing. if the vent door doesn't close it will allow a slight draft to come through the vents. according to my gm buddy its atleast somewhat common for the hvac controls to go bad. he diagnosed my 97 4dr as that when i was having problems with mine. i didnt have a smoky failure stuff just stopped working. it stopped sending out the signal for the rear defroster and a/c signals. i bought a new one off rockauto.

 

[east302]

Might as well pop it open and take a look. There isn’t much back there, just the main harness behind the dash, the antenna and the connectors to the hvac and radio.

I had a new (Dorman) ac panel that started smoking after a few minutes of installation, but the smoke came out around the panel - not the from the CD slot in the player.

Could be the CD player, then. In theory there should be burn marks on the culprit.

With the blower off, some air will be forced into the cabin just by driving. The blower should not be running. Unplug the purple wire from the blower to test that.

 

[doncaruana]

View attachment 239564

So I finally opened it up (I'm actually fighting a cold so that's slowed me down) and I see this. I pulled the CD player and everything looked OK and harnesses on both units seemed alright too.

Popped in the one I got for $20 at the junkyard and things seem to be working with the exception if the 3rd fan setting and there are no lights on the new panel (I don't remember - should there be?).

Is it more likely that I just didn't get the connectors on good or this unit has issues to begin with? Seems like I'd have more issues than that if I didn't get the connectors on good.

 

[east302]

There are six lights, the four gray and two black twist-in socket bulbs in the photo:



There may be two inside for the push button lights but I don’t remember. Either way, you can swap them with the old one.

As for the fan speed, it may be the resistor but if you didn’t have the issue before then I’d suspect the blower switch in the panel. I’m thinking that it’s removable.

 

[doncaruana]

As for the fan speed, it may be the resistor but if you didn’t have the issue before then I’d suspect the blower switch in the panel. I’m thinking that it’s removable.

Not sure I'm gonna mess with the bulbs. Both the one I pulled and the one I put in were both brittle as hell, so I may have messed something up pulling the pigtails out of the "new" one. The one I put in is loose because all the tabs are broke (that's why I got it for $20). I could live with it this way, although I may pull it open again to make sure I have all the connectors snug.

All that being said, you mean the knob/dial for the blower right? (please correct me if not). It is a little touchy. Like I have to give it a little job to go from low to the next position sometimes. Not sure it's worth messing with in the grand scheme.

 

[east302]

Not sure I'm gonna mess with the bulbs. Both the one I pulled and the one I put in were both brittle as hell, so I may have messed something up pulling the pigtails out of the "new" one. The one I put in is loose because all the tabs are broke (that's why I got it for $20). I could live with it this way, although I may pull it open again to make sure I have all the connectors snug.

All that being said, you mean the knob/dial for the blower right? (please correct me if not). It is a little touchy. Like I have to give it a little job to go from low to the next position sometimes. Not sure it's worth messing with in the grand scheme.

Yep, the knob...it looks like it can be removed from the back but I can’t say that I’ve ever messed with it.