Hello All,

I have a 90 Q(fastest one until 2002) and last night my a/c controls went crazy for one I'm unable to turn it off it seems to cycle through all levels. I can adjust the mode and temp. but cannot turn it off, my display went blank about a year ago. Can I repair this or should I just replace the whole unit. thanks in advance.

Everything you ever wanted in a car, is in a Q

I have fixed the display on mine.

I posted how I did it on the old board. Not sure when the old posts will show up here.

As for your other symptoms, I would bet that it is related to a similar problem with the display: cold/weak solder joints on the main control board. Seems like age and heat are the culprits to the problem.

I would bet that J Tucker can fix it if you can't or don't want to bother. He charges like $100 to fix them. I would love to look at it, but I don't have a test bench yet and am not wanting to have to remove mine to use the car as the test bench. Cycling through all levels sounds like a stuck closed circuit on one of the buttons and it is going into test mode.

Here is Jerry Tuckers address :http://www.jerrytucker.net/

Here is Lon's experience...

Decided to attempt to discover the notorious A/C readout failure this Saturday. Disassembled the A/C control box. Tried as many things as I could to no avail. Finally I remembered that one of the posters on this board was able to get the readout to work if he flexed one of the boards. Seeing that the board that has the readout mounted on it does not have that many components on it I decided to try and do some flexing on the main board (the one that plugs into the harness in the dash). Lo-and-behold, if I flexed the board in a certain way while it was attached to the dash harness the readout would start working. I narrowed it down to a one centimeter area on the board that I could put my finger on and push and the readout would come to life. Back at my soldering station I resoldered two different resistors and that was the fix. Hasn't stopped working since. Replaced all the lights and it works like new. Replaced the bulb in the power window cut-off switch as well (that was a task in itself). Had to take the switch apart (snaps together). The bulb in the switch is the same as the A/C backlight bulbs (radio shack $1.49 for a 2-pack). The bulb itself is mounted in a rubber holder that sits on top of two wide pins. The bulb leads are threaded through the holder in such a way that when it is pushed back on the pins the leads come in contact with the pins. One thing I noticed that might be the root of many of the A/C readout problems is that the capacitors on the main board are all leaking electrolytic acid just like the ones on the speaker amps. These caps are from the same manufacturer (nichecon) and are of the same family of caps based on the color of the cap wrapper (brown). When I ordered caps to attempt to replace the ones on my speaker amps the manufacturer representative sent me black caps as the replacement. Apparently the brown ones were prone to failure and this is evident on the A/C readout controller as well as the speaker amps. I cleaned all the dried/hardened electrolytic seepage off of the few caps that there are hoping that this might get the readout working (that was the first thing I tried). I did not have two of the caps in my current supply, so I wasn't going to go through the trouble of just changing one to attempt to fix it. The plan was to order the caps and try the fix at a later date. The test of flexing the board was a last minute test before buttoning it up.

If the caps are the real problem and the solder joints on the resistors are only secondary I will most likely have to revisit this issue at a later date. At least now if it is the caps I have a game plan to fix that when the time comes. I can't see the solder joint thing being a wide spread issue that would effect so many of these readouts, but if there were an issue in the manufacturing process (where a wave soldering device was not applying enough solder or a brittle solder at that) then maybe the whole problem is the solder joints and the caps are only a secondary issue. Time will tell.

Lon Allen - 92 Q45t with a working A/C readout

diesel balls,you ain't got much to say, but when you do...:shocked dayumm

Mayhem_J30 wrote:diesel balls,you ain't got much to say, but when you do...:shocked dayumm

My sentiments exactly! Thanks Dees...

Lon

Listen fellas I thank you for your assistance, but I called J tucker and he had the answer. It's a part called a Heater Resistor the dealer called it an amplifier. the part cost me $85.00 and it is located behind the glove box after you remove the trim. Real easy to replace took about 40 minutes . I'm going to attempt to fix the readout issue this weekend.

thanks again,

"the Q very fast with much Class"