help!!! please!! i have a 90 deville with no read out on the digital display for speedo or fuel dat and climate control.im a good mecanic but some caddis can leave you banging your head. i have a freind in the parts bizz and he gave me a bcm to try.i swapped the prom but nothing?? ive been reading this sites questions and see alot of mention about a centralpower supply? has any one seen this problem?? all fuses are good and i sent the speedo cluster out to be checked and it came back as ok? any help would be great!!!

I have the same problem on a 92 seville changed the bcm and did not fix it

is your display lit ? Mine are lit but only read intermitantly. and my Climate control is dark. When the climate control comes on everything works great
Go figure

allways a caddi:

Did you ever figure out the problem with your 90 DeVille?
I have the exact same problem with my 91 Sedan DeVille, No C or D displays at all.
No lights on the Fuel Data center and Climate control at all. Blower won't work either.
Any help would be appreciated.
thanks

me too, I have an 88 Deville with the same problem. the climate control and fuel center displays are dark, but my blower is still working

sonofernest:

I found my problem to be a bad ground between the harness and the circuit board on the back of the Fuel Data Center, unlike yours however my blower was not working either. That might just be a difference between the years, mines a 91 Sedan deVille. I took the dash apart, unplugged the FDC from the harness and restarted the car, once I did the climate control started working again. I then took the harness with the locking clip facing up and using a light tester pushed both contacts together in order to get a better connection then I plugged it back in. Once I did that everything worked fine again. As you are facing the harness with the locking tab facing up it should be the first connector on the left. I also pinched the other connectors to but avoided the one that was hot, (didn't want to create a short) I can't say for sure this will work for you but it won't cost anything but time to try.

Good Luck!

If your dash flickers and you see a 30sec - 29 second -15second etc on the DIC and your dash dims, goes blank, goes bright etc then its your twilight sentinal switch unit... I refurbished mine myself, its easy...

Regards,
Brian

I tried that and it didn't do anything. However did find 4 dangling wires; a green and a blue one that are wound together and two black ones. I dont think they're causing the problem because the FDC, climate controls, and stereo went out while I was driving and putting down the window. (I already checked all fuses).
I just installed a new head unit the day before and I'm sure that has something to do with it. I unplugged it but there is no change.

Visit Mr. Whizard Technical Services (http://www.mrwhizard.com) for repair of these units.

I am the original owner of a 92 Sevillle STS with 128k dark blue, black leather.
I am experiencing the same issue, no fuel data or climate display with "----" instead of numbers, my window defog comes on when in that mode with cool air.
I have been working on this issue for two months, reading up on maybe's, I changed the ECC with no change.
I have been searching for a ground that is loose and taking apart the dash is the next "to-do".
Thanks CUJO for the information, I printed up your reply and will undertake the dash next weekend.
I will update then.....grin
john

I tried that and it didn't do anything. However did find 4 dangling wires; a green and a blue one that are wound together and two black ones. I dont think they're causing the problem because the FDC, climate controls, and stereo went out while I was driving and putting down the window. (I already checked all fuses).
I just installed a new head unit the day before and I'm sure that has something to do with it. I unplugged it but there is no change.
My '88 CDV did the same thing after an aftermarket radio was installed. Determined the BCM was shorted. The factory radio illumination is not 12 volts as best I can figure and putting 12 volts to the BCM shorts them. reinstalled factory radio and got a wrecking yard BCM. Make sure the new BCM comes from the same year and speedo type. If your speedo is digital, then a BCM from a digital donor, if your car is numbers and a needle type then a BCM from same type. Hope this helps.

John,

I had the same intermittent problem in my 92 Seville. I recently got serious about fixing the problem. I think I might do a write-up on it on my website. But briefly, there a number of things that can cause the dash to cut-out like that. The first thing to check is the ground on the starter. This was such a problem that Cadillac came out with a special ground bracket. My neighbor works at a Cadillac dealer and he says that was the number one problem that caused digital dash to flicker. Don't do any repairs w/o ensuring you have a good and proper ground.

It's important to know that the following modules all communicate on a Serial Data Line:
Powertrain Control Module (PCM)
Air Conditioning Programmer (ACP - for the HVAC))
Diagnostic Energy Reserve Module (DERM - GMs term for the Air Bag system)
Electronic Brake Control Module (EBCM)
Instrument Panel Cluster (IPC)

The key here is knowing that information from the separate computers share information on this "network" in a **serial** fashion. It's a loop so if any one break occurs, it will not necessarily cause a loss of communication (com can go the other direction in the loop). There are onboard diagnostics you can access if you turn the ignition to "on" and hold the "off" and "Warm" buttons down for a few seconds. First all the dash lights will come on and then it will go into the diagnostics mode. Pressing "auto" will take you out of the trouble-code display mode.

Basically on mine, the trouble codes didn't do me any good. My neighbor says they don't often point ya to the problem in his experience. So I resorted to an old trick electronic repair technicians use: a hair dryer and freeze spray. This works on the principal that the majority of electronics failures in electronic devices are due to poor solder joints (cold joints), and leaky or dried-up electrolytic capacitors. This is an ideal trick for intermittant failures like what many on this board describe.

I started out with my PCM. I removed all the shielding and heated it up with a hair dryer. (my dash would fail when the car got warm - after about 1/2 hr). I was not able to make the dash flicker or go blank this way. When the dash did go blank like usual, I used freeze spray (abailable at www.partsexpress.com) to chill the board and observed the dash. It had no apparent bearing on the dash problem. Of course I wiggled connections and all that too.

Next I inspected the connections for the aforementioned computer modules which are located in the trunk behind the back seat. Again, it didn't seem to fix the blanked-out dash. I moved to the last thing, the IPC. I removed the dash pad and drove the vehilce for a while till the IPC would blank out. When the dash would go blank I shot freeze spray through a hole in one end, watched what happened, then tried the other side. I was able to consistantly make the dash lights and gauges work properly with this method. So, time to dig a little deeper.

I pulled the IPC and very carefully removed all circuit boards and taped them to a 3' wooden board with masking tape (to hold the boards from sliding around). I plugged it into the harnass and started the car. Now that I had all boards laying out in front of me I went around with the hair dryer, one section at a time keeping my eye on the dash for any flickering. I moved section by section. Eventually I found a area that would consisstantly make the dash cut out. I heated it up and shot freeze spray in that area. The heat would make it go blank, the freeze spray would make it light and gauges operate properly again. By the way, it was cold out and the dash almost always would cut out after about 1/2 hr. I located the problem in a particular region. I was expecting it to be a bad capacitor. But there were no capacitors in this area.

I tapped around the region with my finger. Everytime I tapped one corner of one of the main processor chips the dash would cut out (go blank). I barely had to touch the corner. But it was unmistakably consistant. I narrowed it down to one pin on that processor. Touch that pin and it would go blank or flicker. I took the whole dash assembly taped to the 3' board into the shop and prepared to resolder that pin. Before soldering, I carefully chipped the clear circuit board protective spray coating (prevent's condensation problems) away from that portion of the chip. I resoldered and tried the dash in the car again. I was not able to make it "blank out" like before. I heated the whole thing up again with a hair dryer and was not able to get the dash to go out. Interestingly, when the dash is assembled, the chip I resoldered would is situated directly behind the power regulator heat-sink (behind the HVAC Controls) which is probably why it would go blank after about 1/2 hr -- the heat would build up in that area.

Guys, this is an example of a trouble-shooting method. It only took me about 15 minutes to locate the problem once I got the dash dissassembled.

Hope it helps.

Mark G

**IMPORTANT**----------------------------------------------------------
1) Before working on your dash, remove your air bag (SIR) fuse and unplug the yellow connector below your steering column. Be sure to discharge static from your body first.

2) Remove the IPC fuses in the trunk before removing your dash

3) This is an example of a repair I made. It may not resolve your problems.

Mark -

Thanks for the detailed writeup - I'm chasing the same issue in a '92 Seville - and was about to undertake the "anal-retentive engineer" methodology that you employed to isolate and resolve the problem (since I am an anal-retentive engineer the reference should be taken in the most positive light!) - thanks for
saving me a bunch of debug time!

Cheers

Steve

If your dash flickers and you see a 30sec - 29 second -15second etc on the DIC and your dash dims, goes blank, goes bright etc then its your twilight sentinal switch unit... I refurbished mine myself, its easy...

Regards,
Brian

Brian -

You don't happen to have a part number OR the "official" name for the part do ya?

Thanks

Steve

I am having the same problem, after installing a third-party head unit in my '86 DeVille, about five minutes into using it, the FDC, Climate Control and Stereo all stopped working, I found it very strange, I replaced the old stereo and it still works. If I short the radio fuse, the displays will flicker and the buttons are still responsive, or at least attempt to be responsive but they won't stay on (if I press the defrost button it will click like it changed but the blower will not go). I have an Analog Speedo and that still operates correctly. Any Ideas?

As I stated earlier, try a wrecking yard BCM (body computer module) same exact thing happened on my 88