that must have been scary!I'm not going to rig anything in my panel. I do not want to mess with an instrument panel from an 80's/early 90's German car. It's scary enough as it is! I just want to swap out the part and move on. I just don't know if its the guages or some relay in the wiring harness or something

Most common failure on these. More than half of the 124/201 temp displays have bleed-out in the LCD like that.

Fortunately, there are more around, I bought two from junkyards.

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Gone to the dark side

- Jeff

Bobman,
I have the exact same scenario (touching clock 12v lead and blowing the tach).
I've replaced every fuse, tried running a new 12v lead, and even installed a new tach. None of which worked.
I've come to the conclusion that its either the OVP or the pickup for the tach (although i'm not sure how it could've gotten affected by the 12v lead).

I'll let you know if I'm able to fix our mysterious tach problem

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1987 300e

-Laziness is simply the act of resting before you become tired

Manich, thanks for your input. I was about to buy a tachometer (if I could find one used). I tried a brand new OVP, and it did nothing for the tach. There could some inline fuse somewhere that blew or burnt a ground or worse yet blew a circuit in the computer. I see that you have a 300E, I'm not aware of the differences in electronics between the diesels and gassers so your solution may vary but it seems unlikely because this a fairly unique problem.

I'm ordering a manual that includes w124 so maybe it will give some wiring diagrams or troubleshooting and i will break out the multimeter and see if I'm getting grounds. My glow plug light does not work and that seems to be grounded through the metal tach assembly itself (all other instrument lights have separate ground wires) so I 'm leaning towards a bad ground. I will definitely look into the tach pickup. I'll let you know if I find anything.