Instrument Cluster****

[Real_ILYA]

I posted a while back on this forum about my electrical issues, and was advised to get the MB Service CD... instead I went to alldata, which turns out to be a pretty good source of info (I guess not much different from the cd, any corrections?), which can be accessed for free at many public libraries (and saved on usb drive)... I also collected the bits and pieces posted on different forums... anyhow...

my instrument cluster was not working for the most part, all dead, except the warning lights and the water temp gauge (they are on separate circuits from the main board in the cluster)... with help of ETP steps from alldata I tested all wiring ok, therefore the cluster itself is determined to be in need of repair... that PCB board inside of the cluster controls a bunch of other functions unrelated to gauges, for instance people report having power top issues that got fixed by repairing the cluster...

after doing some more research, I found out that the problem may be as simple as having to replace one 470uf electrolytic capacitor on the PCB board's voltage supply circuit, the cap can be bought from Radio Shack (SKU#: 272-1030)... so I did that... and I even had a qualified tech-head friend help me just to be sure we do it right... the cap was tested ok out of the box, and the polarity was correct when installed...

so now, instead of a partially working cluster, I have one of those crazy-ass clusters that some other people reported - my interior lights flash instead of the turnsignals, brakelights come on when I open the doors, and all sorts of other insane stuff that I just can't wrap my mind around...

therefore, point being, I thought I'd post this FYI : replacing that capacitor is NOT always a cure... in my case it only made things worse, and now the car is no longer driveable because of crazy turnsignals and other unpredictable exterior lights...

so I will be attempting to find a new used cluster, preferably a digital one, maybe a good mechanical one for cheap, but I might have to just mail mine in to get it properly repaired, it's down to $239 via ebay service purchase nowadays...

the saga continues...

[tecqboy]

If we assume that the original 470ufd cap was good, then replacing it (correctly) with another new good cap could not change the behavior of the cluster. But your experience indicates that behavior has indeed changed. Logic does not allow for this condition. Re-examine your work on the cluster.

[Peter Guenther]

I will reserve my comments, the capacitor in question regulates the voltage to the guages and lights, I suspect you did something when replacing the electrolytic either breaking the foil on the PCB, a new cluster will set you back over a thousand, get yours fixed, dont go on the cheap, deal with a reputable repair provider.
http://mbcluster.com/

[bobterry99]

Originally Posted by Real_ILYA

I...was advised to get the MB Service CD... instead I went to alldata, which turns out to be a pretty good source of info (I guess not much different from the cd, any corrections?)

The MB DVD has schematics that are much easier to read and includes the "Starfinder" application for locating electrical components. I don't think it offers and other advantages.

Originally Posted by Real_ILYA

...I thought I'd post this FYI : replacing that transistor is NOT always a cure...

Replacing the capacitor is indicated when the cluster lights flash with use of the turn signals. I would suggest that it not be replaced to solve any other problems.

[Real_ILYA]

Originally Posted by tecqboy

If we assume that the original 470ufd cap was good, then replacing it (correctly) with another new good cap could not change the behavior of the cluster...

well, one pole of the old capacitor came apart pretty easily (and pretty charred on the inner end), so we couldn't exactly test it, but I believe that indicates it failed internally... in addition, I assume there are probably other failed components...

Originally Posted by Peter Guenther

I will reserve my comments, the capacitor in question regulates the voltage to the guages and lights, I suspect you did something when replacing the electrolytic either breaking the foil on the PCB...

well, that's why I said I had a "qualified" friend do it for me, and since he works on building modern fully computerized Mercedes/Siemens locomotives (that's trains, yes) and deals with soldering electronic components on a daily basis, as well as all sorts of space-age wiring and computer-coding jobs, I thought he passes the qualification condition...

Originally Posted by bobterry99

The MB DVD has schematics that are much easier to read and includes the "Starfinder" application for locating electrical components. I don't think it offers and other advantages.

Replacing the capacitor is indicated when the cluster lights flash with use of the turn signals. I would suggest that it not be replaced to solve any other problems.

That's what I thought about that service dvd thing, thanks for confirming that =)

And I knew that I was shooting in the dark with that capacitor, I figured since it didn't work already, it couldn't hurt... didn't quite expect the results, but that's how working on project cars goes... I just thought I'd share my experience so that it's documented and others may think twice before replacing that capacitor if they don't have the flashing lights issue to begin with... It was worth a try anyway the way I see it, and I certainly learned a bunch about how this monster works