1991 500SL instrumen cluster, roll bar, and soft top. - PeachParts Mercedes-Benz Forum

arr320 · #1 10-17-2002, 12:20 PM

I’m sorry to bother you guy’s but, I have a problem with my 1991 500SL. I have search and found one forum that matches the problems that I have and attempted to communicate with some techs but no luck. I am assuming that the forum is too old.

The problem that I’m having is with the soft top, roll bar and the instrument cluster. All of these devices stopped working at the same time. Soft top and roll bar no response, instrument cluster (fuel, speedometer, tachometer, air temp, economy) stopt working, but interestingly the coolant temp and clock work fine. The cluster lights up okay and the idiot lights below the cluster seem to all work, but every thing else ‘nada’!

I have checked, and swapped, the main fuses with no luck. Also have pulled the cluster and checked the plug connections, re-seated the CIS, again with no luck.

Any help greatly appreciated...

mbdoc · #2 10-17-2002, 05:03 PM

The soft-top fuses are in the trunk.
The instrument cluster is powered from fuses 5 & 9 in the front fuse box.

ILUVMILS · #3 10-17-2002, 08:47 PM

Older SL's hate being jump-started. The soft-top/rollbar ECU seems particularly susceptible to damage from voltage spikes. I've also seen IC circuit boards suffer the same fate.

Gilly · #4 10-18-2002, 12:15 AM

Did you also check the fuses in the Base Module?

Gilly

mbdoc · #5 10-18-2002, 08:26 AM

A 1991 500SL doesn't have a base module!! That didn't happen until 1993 ON the 500SL.

arr320 · #6 10-18-2002, 09:08 AM

Wow, thanks for replying guys.

M.B. DOC I have inspected and exchanged all of the fuses also the ones in the trunk.

Iluvmils I suspect that the whole problem started with the passenger window. After attempting to lower the top I noticed that the passenger window was inop. My first instinct was that the fuse in the trunk was blown. Yes, I was right the passenger window fuse was blown. Immediately I replaced it with a new one, and attempted to lower the top. While doing this is when I noticed all of the problems. By the way Iluvmils, what is “ECU” and “IC”?

Where might the Base Module be located at and what does it do Gilly? I herd people mention it a couple of times.

Thanks for all your help guys, I’m sure I will be able to locate the source of my problem with your in-depth knowledge.

Becky

ILUVMILS · #7 10-18-2002, 06:26 PM

ECU= electronic control unit( located beneath storage area behind passenger seat ) IC =instrument cluster ( you know where that is ) By the way, if the cluster is fried the electrical portion is available as a spare part. good luck

Gilly · #8 10-18-2002, 09:49 PM

Becky:
I suspect MB DOC is correct on this model not having a BM (Base Module). A basic description of what the BM does is distribute power to other modules and protect the modules it provides power to from overvoltage conditions (voltage spikes).
If it had it, it would be on the passengers side of the vehicle towards the rear of the engine bay inside what is called the control module box. On top of the BM is a small plastic window which can be flipped open (hmmmm, maybe it's a door not a window?) and there is some fuses located under that door. I've seen instrument cluster components go dead from a blown fuse in the BM, and also can be the source of other various problems, such as a diagnosis computer (mechanics diagnosis tool) not being provided power from the diagnosis plug on the vehicle.

Gilly

arr320 · #9 10-21-2002, 09:47 AM

Thanks for replying guys.

I’m sorry I haven’t responded sooner; it’s because I was out of town this weekend.
Well, any way’s is there a way for me to test out the system to see what’s working and what’s not? I have been told that my SL has two top control units. I know where one is located (behind the passenger storage compartment), but where is the other one found. Is there some thing that all of these units use in common, a relay or some sort?
P.S. where is the roll bar control unit located?

Thanks Becky