Digital Dash Repair Tips:
Digital clusters can be problematic in Cadillacs ...and other cars. It seems there is a deficiency of good troubleshooting info, or it is scattered in several posts. Hopefully we can get a thread going that will be useful for those who want to "hunt" down and resolve problems w/o paying a king's ransom. I invite others that have resolved dash problems to share their troubleshooting methods. If enough information is added, perhaps this can be a "sticky" thread to help others.
Problem: For me, it all started with an annoying intermittent cluster problem in my 92 Seville that became more and more pervasive. Here were the symptoms: After about a 1/2 hour or so of operation, the cluster would go completely dead, all needles flatline and radio light blank. The fuel data and HVAC lights would flicker and finally go blank. As a result, the HVAC system would go into a default defrost mode and 75 degrees heat (annoying in the summer and winter).
Finally, I got serious about fixing the problem. Since it was an intermittant problem I figured it would be relatively easy to spot and resolve. The following article is the steps I took to do that. I have some very basic electronics repair experience which helped, but anybody with decent mechanical skills should be able to apply the same strategy. I may might do a more detailed write-up on on my website (
www.RepairNation.com) in the future with some pictures.
There a number of things that can cause intermittent problems like this: The VERY first thing to check is the ground on the starter and body. This was such a problem in the early 90's that Cadillac came out with a special ground bracket to retrofit cars with. My neighbor works at a Cadillac dealer and he says that a bad ground was the number one problem that caused digital cluster to flicker. Don't do any repairs w/o ensuring you have proper grounding.
It's important to know that the following modules all communicate on a Serial Data Line:
PCM - Powertrain Control Module (the ECM)
ACP - Air Conditioning Programmer (for the HVAC))
DERM - Diagnostic Energy Reserve Module (GMs fancy term for the Air Bag system)
EBCM - Electronic Brake Control Module
IPC - Instrument Panel Cluster
Information from these separate computers share information on a **serial** data link to the cluster. It's a loop so if only one break in the circuit occurs, it will not necessarily cause a loss of communication (com can go the other direction in the loop). But issues with one module can have rammafications with the performance of the dash/cluster and that makes it particularly challenging to troubleshoot the system. To pay a Cadillac dealer to track down dash problems will most likely cost a prince's ransom. Fortunately, there are onboard diagnostics you can access that may aid in pinpointing some problems. To access the diagnostic mode turn the ignition to "on" and hold the "Off" and "Warm" buttons down simultaneously for a few seconds. Initially, ALL the lights in the cluster will illuminate (test mode) then it will go into the diagnostics mode. Record the trouble codes if any. Maybe someone would like to post the codes and what they mean. 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 who has worked as a mechanic at Cadillac for 15 years says they don't often point ya to the problem, in his experience. To pinpoint the problem I resorted to an old trick electronic repair technicians use that involves careful use of a hair dryer and freeze spray. This strategy works on the principal that the majority of electronics failures are due to poor solder joints (cold joints), and leaky or dried-up electrolytic capacitors. This is an ideal trick for uncovering intermittant failures.
Getting Started:
I started out with my PCM. I removed all the shielding and heated the circuit board up with a hair dryer while the car was running. I was
not able to make the dash flicker or go blank this way. When the dash did go blank after some time (like usual), I used freeze spray (abailable at
www.partsexpress.com) to chill sections of the board and observing the effects on the dash. Chilling board or components on the board had no apparent bearing on the dash problem. Of course I wiggled connections and all that too, to no avail. I put it back together and moved on.
Next I inspected the connections for the aforementioned computer modules which, in a 92 Seville, are located in the trunk behind the back seat. Nothing I did back there seemed to have any relavence on the blanked-out dash (or made it flicker when it was actually working). I moved to the last thing, the IPC - Cluster. I removed the A-pillar covers, then the dash pad to reveal the cluster. Then I drove the vehilce until the IPC would flicker or blank-out as usual. When the dash would go blank I shot freeze spray through a hole in one end, watched observed the effects, then did the same to the other side. I was able to consistantly make the dash lights and gauges work properly with this method. At this point, I knew the problem lie in the cluster electronics. Time to dig a little deeper.
Working on the cluster:
I pulled the IPC from the car [see notes below] and very carefully removed all circuit boards from the cluster housing, and taped them to a 3' wooden board with masking tape (to hold the boards from sliding around). I transferred the whole assembly back to the vehicle, plugged it into the harnass and started the car. Now that I had all boards laying out in the open in front of me I could do some real diagnosing. I went around with the hair dryer, one section at a time keeping my eye on the dash for any flickering. I worked section by section. Eventually I heated up an area that would consistantly cause the dash to blank-out. Shooting freeze spray in that area would make it operate properly again. I was expecting the problem to be a bad capacitor. But there were no capacitors in this area.
Investigating further, I tapped around the region with my finger [be sure to discharge static from your body beforehand, or wear a wrist strap]. Everytime I tapped one corner of one of a particular processor-style chip the dash would cut out (go blank). I barely had to touch the corner. It was unmistakably consistant. I narrowed it down further to one pin on that microchip. Touch that pin [with a plastic instrument] it would go blank or flicker.
Making the repair:
I moved the whole dash assembly taped onto 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 carefully resoldered not applying too much heat (which could damage the microchip) and connected the dash to the car again. I was not able to make it "blank out" again. I heated the all circuit boards again with the hair dryer and was not able to get the dash to go out. Interestingly, the chip I resoldered resides next to the power regulator heat-sink (behind the HVAC Controls) when installed in the cluster housing. The heat produced by the regulator would cause a minor amount of expansion which would move the poorly soldered joint enough to break the power connection and cause the dash to blank-out.
The repair has been a success so far. So, guys, there you have it - an example of how a specific oft-used electronic trouble-shooting technique was used to isolate and resolve a pesky digital cluster problem. It only took me about 15 minutes to locate the problem once I got the dash dissassembled.
Other things to look at:
There are a bunch of electrolytic capacitors and what looks like a switching or regulating transistor on the power regulating portion of the cluster (behind the A/C controls). I can see how these could be a source of cluster problems that one would want to investigate in the course of a digital dash diagnosis. Capacitors often leak and/or dry up over time. These are high quality capacitors but 10 years is a long time for these and cars get hot in the summer. Look for leaky or bulging (tops) features. They could easily be unsoldered and replaced if found to be faulty (capacitors are marked for size and capacity). Newark is a good place to buy replacements electronic parts.
Hope this helps. Please share your tips and experiences.
Mark G
**IMPORTANT**----------------------------------------------------------
1) Before working on your dash, remove your air bag (SIR) fuse and unplug the yellow connector below your steering column.
2) Always be SURE to discharge static from your body before messing with any electronics or your car's Air Bag, SIR system. Wear a wrist strap or just tie some wire to your arm and ground it at the other end. You can never be too careful.
3) Remove the IPC fuses in the trunk before removing your dash. Reinstall after hooking your dash back up.
4) This is an example of a repair I made. The techniques used may not necessarily resolve your problems. Any repair attempts are made at your own risk :disappoin
Digital Dash Repair Tips - Ideas how to resolve speedometer and cluster problems 
but i did make 1 mistake
i used a voltage w/a little light bulb checker to chek climate conector for ground because i had juice i taught i might have been loosing ground. found the ground,but in the process did some thing now its on but the dic shows two rows of dots 1 on top 1 on bottom still work thoug and it added a 1on the otside temp now it read 129f but atleast i have heat would of helped in the ice storm we just had
wasnt hard 2 trouble shoot thanx when i find my problem i will post it
