While driving my 1995 300D to get the Lemforder flex discs my tachometer started working intermittently then not at all. The darn thing only last 18 years! Any suggestions?

There is a relay, can't remember the name right now. A/C won't work without it. First thing I did to my car when I got it.

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The Overvoltage protection relay has one or two fuses on it which will cause the tach to go dead and a bunch of other stuff not to work.

Its behind the battery, it will be a tall silver relay with a door on top.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Thanks guys, anyone know where this relay is located on the car?