Cadillac Repair/IPC Blackout


Hello.  I have a 1992 Cadillac Brougham.  I bought this car over a year ago.  When i test drove it, i noticed the IPC didn't light up.  Well I tapped the lens with the tips of my fingers and it came on.  It stayed on for a while, meaning several months, with no problem.  Then, one day, while driving, It just went off.  I tapped it again like before and it would come back on.  Sometimes it would go off as soon as you tap it on.  Well a week ago i was driving and it hd been giving me a fit all day.  The next morning i went out to start the car and the IPC was off.  I tapped it and nothing.  I tapped a bit harder and still nothing.  So i checked the fuses and they was ok.  Then I took the IPC out and checked the wires.  They was ok.  Everything else like the dash lights and climate control panel still works fine.  Its just the IPC.  Would the IPC Relay have anything to do with it just quit working?  I thought I would ask before trying to replace the whole cluster.  And if so where is it located?


Worst case--

As reading your complaint I already decided what most likely was the problem. I believe you have a cracked PC board in the IP.
You will find that weather will effect the lights as well. All you need is a hairline crack. Remember, this plastic is over 23 years old. Hot and cold, vibration. The fact that tapping the lens and the lights would work s telling. If a relay fails, sticking open or closed, it stays that way and it was obviously not a fuse and couldn't be. Once blown, its blown and tapping the lens would not make a difference.

Over the years, I have occasionally run into cracked PC board in the cluster and one can get the crack to go back together for a while tapping the speedo lens. I imagine it is small enough that even if you were looking at the back of the cluster, you might not see he crack.
If you had a factory service manual, which I always recommend for questioners to try to get from Craigs or Ebay, you could check the schematics on the cluster and use an ohm meter to determine where you have an open, but even at that, there is no way of repairing.

Before you dive in and go to a junk yard for a cluster, consider this--you could have a loose ground. Again, the manual is the source to tell you where the grounds are. You can go under the driver' dash and look for ground points. You will find areas that have numerous black wires with a bolt going through their eyelets.

Doing electrical diagnoses without a factory manual is working in the dark and an be difficult to fix without knowing where each wire goes from the cluster. Remember as well, the manual would be used for all future repairs and save you a boatload of money.

Personally, I do not change parts on a guess. I have supplied you with the two most possible causes.

Please let me know what you find.

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Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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