Hello Everyone,

Alright, well, I never really got much time to work on the car this weekend...

Here is my question:

The tachometer does not work at all, but the clock does, do the clock and tacho share a common grounding within the cluster? Or are they separate?

Another thing:
My father told me that the tacho acted up when he took it out on the weekends while I was gone, he said he 'tapped' the area right above the cluster. (Then he later told me he 'hit' it! lol ) and the tachometer would jump up and then suddenly give the correct reading... then after a while would die again.

I drove the car tonight a bit, I gentle bumped the area on the dash above the tachometer and the needle would jump to like 200 RPM and immediately fall to its resting point... (Car was running, did this in the driveway.)

Is there a common failure with the tachometer in the cluster itself? (1989 300E W124 era)

I found a cylinder looking thing with a cap that had a strap to make sure it is not lost. I opened the cap but all I saw was some kind of diagnostic port.
(Next to EZL unit)

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)