on my w124. the car sat for 3 yrs with periodic cranking . A couple of weeks ago I cranked it using jumper cables mistakingly crossing the posts for just a touch. Corrected that and fired up the engine but the abs light was on and the tach didn't work. Several people on the forum suggested the ovp fuse. I replaced the fuse and the ovp now the light is off but the tach still doesn't work. Any other ideas on why the tach does not work?Bye the way, the fuse was blown in the ovp
thanks in advance

Check the OVP again? could have blown the fuse on the new one if there's something amiss on the system.. Check the grounds in the cluster and the grounds in the engine bay

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

You might need to replace the OVP. Sometimes they go bad and the fuse is still good. It will effect the tach, ABS, and A/C circuit as was my experience.
Good luck!

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Western NC
1987 300SDL W126 Turbo Diesel 335,000 + miles
1976 300D W115 275,000 miles+

x3 on the OVP relay. Jumping the car can sometimes fry them, as I found out on my 85 SD with ABS.

Check the circuts on the back of the instrument cluster, they can burn out. My oil pressure gauge stopped working after a voltage surge, it had burnt one of the copper strips away. A bit of wire and some solder later, and all is well.

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87 w124 zender 3.6 - 3.0 kompressor in progress!
96 w124 e300 diesel - slowly being modded
98 w208 230 kompressor - m103 testbed SOLD.
96 s124 om606 superturbo diesel 508bhp

I hooked a charger up backwards to my '87 during winter storage and lost the OVP fuse and the SRS system, I think that the tach was out of the car though.

Check for the SRS light also, which probably means you need a new voltage-converter in the passenger side kick-panel.

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Gone to the dark side

- Jeff