Fuel Data Center - Odd Behavior

[guyslp]

I have now had this same peculiarity occur twice. It is only the fuel data center that's misbehaving.

It will randomly start cycling through all its own settings, MPG, Avg MPG, Range, etc., with no rhyme or reason. The last time I cured the issue by doing a "hard reset": disconnecting the battery for a while then hooking it back up. This returned it to normal function for at least several weeks.

Has anyone else ever experienced this behavior and know its root cause?

Brian

[rockfangd]

This is on the 89?

how does the button feel. It may be worn and be too sensitive at times

[guyslp]

The only Cadillac I have at this time is the 1989 Sedan de Ville.

I guess it could be a button issue, but I truly doubt it. When I have needed/wanted to use the buttons (and the unit isn't in one of its "spasms") they all behave quite normally. None require extra heavy or ultra light touch.

This issue also pops up at random and when I haven't touched the fuel data center in ages.

Brian

[Cadillac Jim]

It sounds like a short in the wiring harness, or a loose connector on the dashboard module.

[KHE]

It sounds like a short in the wiring harness, or a loose connector on the dashboard module.

More likely it is loose/fatigued solder joints on the fuel data module.

[guyslp]

Given my experience with bad solder joints on other automotive electronics I'm suspecting that's the most likely culprit.

If the wiring that goes to this thing is anything like what goes to the window controls in the doors it should be tough enough to last through way more than 25 years of use. That being said, one can never discount possible wiring issues, but they're option two in this case.

I really appreciate the assistance and brainstorming. Yesterday I went from functioning normally to whacky cycling while driving. Just as an additional note, it's only the left side of the center that deals with MPG and range related stuff that's gone off the beam. The gas gauge function at least appears to be OK. I'll see when I go to fill up.

Brian

[guyslp]

I just thought I'd give an update.

The fuel remaining/gas gauge function appears to be working as accurately as a digital one can (which is far from perfect, but more than good enough to know that you have some fuel left or are going to need to fill up).

The mileage and range functions continue to intermittently flake out. One thing that I've observed is that this is much more frequent (though still not anywhere near to a daily thing) when the weather is hot and the interior temperature has been high. Once it starts doing the crazy cycling thing it keeps going, even if you run the AC for an extended period. At some point, always after turning the car off and starting it again, it "heals itself."

I'm really more convinced than ever that this is likely a solder joint failure. I was over at our "pull the part yourself" wrecking yard the other day and took that opportunity to remove most of the dash trim on a 1993 Sedan de Ville, which has the same dash setup as the 1989. It was surprisingly easy to do. The only "trick" in the whole thing, which is not at all well documented in the Service Information Manual is that you remove the small trim piece beneath the steering column by gently pulling/prying it out from the bottom - no screws are involved. You have to do this before you're able to remove several of the screws that hold the larger panels on that flank the upper half of the steering column on each side. Once those are off, it's just two screws securing the fuel data center and the single wide, flat slide electrical connector on the back. Now the challenge will be seeing if/how one can remove the metal case around the PCB so that the solder joints can be checked. I would have purchased the one I removed, but they wanted a bit much for it and, post 1989, it reads Premium Unleaded Fuel Only and the 1989s can use regular and note Unleaded Fuel Only.

Brian