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Cadillac Repair/digital dash on a 86 cadillac fleetwood


QUESTION: Why won't my digital dash work nothin is lighting up neither my speedometer or climate control or gas information but all other lights work jus nothin digital reads! Its a 1986 Fleetwood fwd

ANSWER: Hello,

Please remember,I am not at the car and I have no idea of its repair history over 28 years. I assume you are speaking of the FWD model.The first thing I would check though would be the gauge fuse. In fact, check all the fuses. lo be are that Cadillacs are known to have more than one fuse box and its best to look at the owner's manual for location.
Did this problem just start? Has it been that way for a while?
Get back to me.

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QUESTION: No fuse seem to be blown n I've had a problem with the Speedo not workin right for awhile but the climate control n gas usage jus stopped working today..the Speedo works when car runs at a idle for 15mins it will read but it jumps around..but if car isn't warm will not read

ANSWER: Hello,

See, tat is why I asked what I did. People have a tendency of leaving out important details, like the speedo was giving you issues before and now you are having a temp readout issue.
There are many things that can be wrong with the speedo and it may not even be related to your latest problem. Guessing is just going to cost you money and frustration.
These speedo instrument panels were commonly defective new with broken circuit boards internally. You could have a bad speed sensor located behind the dash. There were no speedometer cables in this vehicle.
You could have a bad connection or a bad ignition switch (not the key cylinder) but the electrical ignition switch under the dash at the top of the steering column. Since everything is plastic, a number f grounds are located under the dash and you could have a loose ground, or there could be a ECM (Electronic Control Module-computer issue or a display problem in you heater-A/C.
Sounds complicated doesn't it? It can be.I just don't want you replacing parts on a guess without actually repairing the problem.
Another issue is very few shops and even the dealers (Don't want you going there) have no reference manuals or information for a car this old.
What you need to do before doing anything else is to purchase a 1986 Cadillac DeVille factory service manual from Craigslist or Ebay. There are step by step diagnostic flow charts to guide you as to exactly what the problems are. If the Speedo unit is bad, you may and up going to a junk yard and going through 2 or 3 before you find a good one. If the ECM is bad, you can go to and they have many of the electronic parts like speed sensors. If the problem you have is in the temp display, that will have to be obtained at a junk yard.

Computerized vehicles were really neat when they came out in 1980-until problems developed. These cars are not like an old 60 Chevy where someone had a problem and the repair was always the same. You are dealing with old electronics here where they have been subjected to extreme heat, cold and age.

You will find the factory manual the most valuable tool for repair of this vehicle and without it, the problems will not be properly diagnosed by anyone, especially on the Internet and not being at the vehicle.
I know Cadillacs very well, having worked a a tech and service manager at GM dealers for 11 years and another 17 repairing these vehicles as theft recoveries. I have owned over 20 Caddys and love them, even with their inherent problems.

You might find the problems may be as simple as tightening a ground under the dash, or more severe.

Good luck!

---------- FOLLOW-UP ----------

QUESTION: Well I got my dash lights back n my climate control n the gas info..there was a break in the wire I fixed it n now all lights work..but Speedo only works when it wants to..n thank u very much you have been very helpful..


What was real common with the old digital dashes were circuit boards inside them that would crack and and weird things like ambient temperature on the inside of the vehicle would effect them. Say it is cold or cool in the vehicle. Speedo won't work. Warms up inside the vehicle and speedo working fine. What would happen is that the warmth would cause the printed circuit board to expand, there by closing a loose connection.
All the early GM digital speedo units had issues. Common warranty for the Chevy Blazers, Cadillacs, Pontiacs, Olds.
Dealt with it on a daily basis in the 80's and into the 90's. That is why I preferred Analog, although that choice was gone.
I am really glad you found your problem of being a wire. Please take my advice though, get a factory manual, commonly costing about %50.00  It too, would have directed you as to exactly which wiring to check.
I was correct on one point. Two separate unrelated problems.

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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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