Can't lower temp with climate control

[MCNE]

This is a strange problem. I can raise the temperature but I can't lower it so it eventually gets stuck at 90 degrees. I've tried going into the diagnostic mode to view the codes and I'm not getting any error conditions. No errors at start up either. This problem seems to come and go. I currently have the battery disconnected to see if that works.

I guess the control unit could be bad?? No other problems with it other than that.

(1996 coupe)

 

[MCNE]

All is well now after reconnecting the battery. Hope it's fine for a while.

 

[ediconu]

MCNE, mine does the same exact thing.

According to older posts on this forum, the Head Unit for the Climate control freezes. Sometimes mine won't go into certain modes (auto/recirc/vent) and a TON of times, it won't let me change the temp up or down.

I'm not sure what's going on, but I know that others have said that replacing the Head Unit fixes it. I was looking in the shop manual and it said nothing about the unit freezing up, or any way to troubleshoot it.

The other posts have prices for head units, just seach for climate control.

Mike

 

[ediconu]

I was just remembering something from the shop manual that said that the logic can get messed up so that it won't act right. This may be what we're both experiencing. I am at work now, but when I get home, i'll get you the instructions for resetting the logic.

It may be as simple as disconnecting the battery for a few minutes, as you've already done.

 

[JT ZR-Won]

All is well now after reconnecting the battery. Hope it's fine for a while.

Weird things can happen from just unplugging the battery. I've had it fix an AC problem in the past also

Jay

 

[ediconu]

JT ZR-Won-

Were you able to fix it by resetting the logic or did you have the actually replace the head unit?

Mike

 

[JT ZR-Won]

Luckily I didn't replace anything. One day the AC just stopped blowing cold air. The motor works fine though. After I reconnected the battery it somehow resets itself and all has been fine ever since.

Jay

 

[MCNE]

It is strange. The funny thing is I only have problems with tht one function. I drove the vette to work today and although it has really cooled down here I played with the temp setting along the way and didn't have a problem. I did have it reset one time by just going into and exiting where you view the codes.

 

[69MyWay]

MCNE---common problem.

It can occur for a variety of reasons.

Believe it or not, jump starting another car with the Vette can be hazardous to the head unit.

How do I know....? Nikki jumped off a car with her old vette and the EXACT same thing happened. We had to replace the control head. It was about $150 and an hour total to yank the dash trim, swap it out, and slap it back together.

 

[ediconu]

Is there an easy way to pull something out to disable the connection to the A/C head unit if you do have to jump-start the car? (or another car, i'm not sure how you meant to word that)...

-Mike

 

[RonV87]

Mine did this - There are quite a few posts on this subject in this forum. Do a search for more info. Before you replace the climate control head, pull it out, take it apart and clean all the connector pins/sockets, particularly the ones betweet the big horzontal PC board and the small vertical one. Also clean the contacts on the PC board under the membrane switches. Be careful not to lose the "buttons" in the rubber piece that lays over the vertical board. Also check the boards for cold solder joints and reheat any. There is a very good chance that this will fix your problem for years.

 

[froggy47]

If it comes back you may need to replace the hvac controller. My 96 was doing that stuff & new controller fixed all.

 

[MCNE]

Thanks for all of the replys! It looks like it's holding for now but I will investigate the cost of a new unit just in case. I wish I had more time to actually drive the car now that I have it for this to be more of an issue.