dead gauges - PeachParts Mercedes-Benz Forum

cricomac · #1 07-02-2003, 07:25 AM

Greetings to all.

All gauges (except oil pressure) have failed in my 91 500SL. Don't know if it's related, but the clock ran slow for a couple of days -- all worked fine yesterday, but this morning the entire instrument cluster is DOA. Idiot lights appear to function normally, based on flashes during startup. Car runs and drives normally. I've checked fuses, but don't find one blown. Any suggestions -- or is this something I need to refer to a dealer? I've searched the archives, but couldn't come up with matches to this problem.

Thanks much,
Scott

cricomac · #2 07-02-2003, 12:35 PM

I misspoke in the previous post -- it is the coolant temp gauge that continues to function, not oil pressure. Everything else is dead.

Scott

mike690003 · #3 07-02-2003, 06:18 PM

Re-check the fuses! I swear those fuses can look fine, but upon further inspection, there could be a hairline crack on the fuse.
If that fails, then its time to pull that cluster out and look for a burned,frayed, or damaged wire.

cricomac · #4 07-02-2003, 10:12 PM

The saga continues...

The convertible top will also no longer retract. There is a common demoninator here somewhere -- any ideas?

Scott

LeaUK · #5 07-03-2003, 05:12 PM

It's a long shot but the hood fuses are in a fuse panel in the boot (trunk). Have you checked them?

tecqboy · #6 07-03-2003, 05:35 PM

Electrical problems are the hardest to diagnose from a distance. But, all those items not working could not be just one bad fuse. I'd start looking for a bad connection around the battery. There is a short connectiion ( wire ) between the negative battery post and the car frame in the trunk. Is it corroded? There is also a cable between the engine block and the frame someplace ( I have a 300SL so I don't know where it is on a 500SL ). The battery cables can corrode under the plastic insulation and look OK on the outside but be bad inside. My personal experience was a corroded positive battery cable which looked OK but was a mass of green powder inside. Keep us informed. Tod

Ronbo · #7 07-10-2003, 03:50 PM

I just happened to be browsing the SL forum and happened to notice your post about dead gauges. That rang a bell since I experienced the same problem on my 92 500SL.

The problem turned out to be a dead microprocessor on the instrument cluster panel. I tried buying a used one but had no luck with that. There is a voltage regulator on the board that can give the same symptom but mine was OK. I wasn't able to find anyone that would trade for a rebuilt board. I ended up paying over $1000 for a new instrument cluster from Mercedes.

I couldn't get my top to work either, I think that the microprocessor decides whether you can put the top down based on a number of things including zero speed which comes from the processor (maybe). Anyway, after I replaced the instrument cluster, the top works fine. I also had some problems with the power sreering (also speed related?). I found that the instrument lites would flash in a particular pattern (I don't think that they normally flash) it is trying to tell us something.

The root cause of this problem, I think, was the use of a battery charger without disconnecting the battery (like the manual says) by a hamhanded mechanic.

Good luck
Ron