I am copying my response to another thread here, hoping to get some help!!

The following describes my experience with temperature adjust buttons (and other buttons) on the Climate Control on my 96 LT4:

Your description of UP button working sometimes and DOWN button working other times (as well as intermittent operation of other buttons) is identical to my experience. It appears to change from one set of working buttons to a different set of working buttons when the ignition is turned off and back on. Occasionally all buttons work fine. These changing symtoms seem to indicate that the problem is not in the front panel, but rather in a connection or possibly in a solid state component (perhaps a timing issue) on the circuit board inside the control box. Cleaning the front panel contacts may disturb a bad connection sufficiently to make contact again and cause all buttons to work (at least temporarily).

I would love to know if anyone has tracked this rather unique problem to the source. It would sure save me the headache of trying to track it down.

 

All I know is my 94 would work sometimes when the buttons were pushed and sometimes not .I replaced the whole dash panel buttons and it works great now.

 

i have the same problem in my 96... :*(

 

My '96 started with trying to turn down the fan speeds working at times and later having to push on or off button many times before they worked this is an old thread of what fixed my problem cleaning the contacts on the circuit board...http://forums.corvetteforum.com/show....php?t=1144275

 

My '95 did/does the same thing. Replaced the head unit couple times now. Fixes the problem for a short while and then it comes back. I asked Gordon Killebrew in Eureka Springs about it and he said it was not necessarily the head unit but another module inside. Unfortunately, my controls were working at the time so I did not pay that close attention and now don't have a clue.

 

Thanks for the responses... Every bit helps... Its obviously not an isolated problem!...

I guess I will have to dig a bit deeper (find the 'other module inside', etc.).

I'll let y'all know when I find the source of the problem.

 

Our 94 did the same thing, but found Forum advice back 2 years ago that advised what to do.

Basically, just remove the control head, gently take the front panel off. You will find a rubber membrane with carbon 'buttons' on the backside which contact the circuit board behind. Clean the carbon buttons (e.g. alcohol) and the circuit board contact points (pencil eraser) and reassemble. Has worked flawlessly since done 2 years ago.

Hope this helps.

 

Its either the head unit or an item called the MEM Programmer. I have had this problem before and the fix is easy just expensive. If the buttons are not working its your head unit. If you are running the AC and it goes from hot to cold and back and forth or it does not work in auto mode its the programmer. The programmer is under the drivers side knee pad area. The problem is it is expensive at a dealership its about $1000, from GM parts direct its about $600. I have not fixed mine yet either, since they seem to only last about three years in my car.

John

 

Mechanicalman,

I understand your frustration and sympathize with your desire to find the source of the 'problem' .

Albeit electronics are unavoidable, an automobile environment is definetly not the best place for them and can cause odd problems.

However, the 'control head' is not just a set of switches, it is actually a small computer in its own right.

The connection to the 'programmer' mentioned by 'LTjuan' is only via 3 wires, an '8' volt reference and 2 'data' lines. It's the 'programmer' which does all the actual work of switching the fan speeds, air direction, etc.

Therefore, if the control head 'computer' doesn't get correct 'instructions' from the buttons via an albeit momentary, but consistent voltage and not incorrect/confused voltage signals due to dirt, it cannot send the correct 'data' to the 'programmer'. It might also mis-interpret the voltage signals and cause the 'reversing' symptom described by many.

Perhaps you have heard of the computer adage 'GIGO', garbage in, garbage out. It unfortunately applies here too (i.e. if the 'control head' feeds garbage to the 'programmer', well then...).

Lastly, I only cleaned the 'control head' rubber buttons/circuit board, and whereas before, I couldn't select 'auto', could only go up on fan speed and not down, and temp set didn't want to go down, it has continued to work FLAWLESSLY now for 2 years after the cleaning .

Hope this helps..

 

I again appreciate the good and indepth advice... You folks have obviously dug deeper than the surface on this problem. Mr. Admiral, your description of the symptoms fits my experience (and other's as well) to the "T"...

I am quite familiar with the membrane switches behind the front panel since this is the first thing that I took apart when looking for obvious reasons for the failure. I was really expecting to find a cold solder joint or something similar that would explain the failure of a certain set of buttons one time and an entirely different (yet consistent) set of buttons another time. Generally, on this type of input several buttons will share a common circuit (multiplexed) so that a cold solder joint or bad connector joint will affect a certain set of buttons... But I found nothing obvious.

I will certainly try the time tested "eraser trick", but I'm wondering if the real culprit may be in the many pronged connector between the front button assembly and the circuit board. Here's why: It now appears that all buttons are working normally (at least for the moment!) after taking this apart and putting it back together. One possible explanation: The circuit baord is fastened to the back of the "control head" cover by two screws. I wonder if the wide fluctuations in temperature that typically occur in the dash environment might cause some slight expansion/contraction of the cover, thereby causing movement (or flexing) of the connector to the front panel. Perhaps over time, the desired "air tight" metal to metal contact between pin and connector is disrupted (it wouldn't take much) on at least one of these pins.

Oh, well... I guess I'll know in another week or so if buttons continue to work. If so, I'll take it apart again and give both membrane switches AND the connector & pins a proper cleaning!

Regarding the behind the dash "programmer", all system outputs (fan, heat, AC) seem to function and control properly, so I think I'm OK here...

Thanks again for the good advice!

 

My 96 did this when I bought it. I "fixed" mine and found it was a vacuum issue and not the head unit. I replaced the vacuum lines and the ones going to the cruise control. This also fixed a bad idle after warm up. Maybe, Maybe not the fix.. Cheap to try.

 

NEVER EVER use an eraser on gold plated circuit board traces!!!!!!!!!
Wipe the trace with alcohol and a cloth. The gold plating does not oxidize or corrode and the plating is extremely thin and an eraser can remove the gold leaving copper. Now if you want constant trouble with a circuit board connection, remove the gold plating !!!!!!!!!!!!!!!!!!

 

Yup my 94 has been doing this for years!Funny thing is,it acts up when hot outside,now in the cooler month's it's always worked good,So in the sometime I set it,& try not to play with it,aww yes the joy's of owning a C-4,LOL.

 

My '95s temperature UP button is sometimes troublesome. My wife hates it when she turns the A/C on in the summer then tries to turn the temp up in the evening.

 

Several days now and the Climate Control head is still working fine! All I did was take it apart, inspect it closely and then reassemble (NO cleaning whatsoever!). This tends to point to a faltering contact connection on one (or more) of the connector pins between the front button module and the main circuit board. (Refer to my wordy description in previous post.) Dissassembling and reassembling this connection has apparently reseated the faltering connection and given it (at least for a time) a new lease on continuity!! Or so I hope...

If it fails again, I will take it apart and give it a proper cleaning!

 

Where is a good place to get parts to rebuild the climate control?