Hey all,

on my 1980 300SD and my 1981 300D, both of which have the same left-hand instrument item (with temp, oil pressure and fuel gauges), the gauges sometimes jump a little higher than they should be, but if I give the dashboard a few knocks they jump back down (and up again, if i keep hitting it). Sometimes tapping the horn causes the gauges to do their little jump up or down, other times it doesn't do anything. I notice that when the temperature and fuel gauges are lower, the effect is more pronounced. Any thoughts on what would cause this? Anyone else experience it?

Thanks

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1980 300SD (daily driver), 1981 300D (Inca Red)

Well, you need a better ground hook up on your gauge panel. You can make one easy, it even helps a lot if the screws that hold your three sections together are very tight and maybe rough up the surface where they overlap because the grounds run through the back panel. "Techman" on the Forum even sells a little harness to help the ground, though it is easy to make one.
http://www.mbelectronicupgrades.com/Tachometer_Amp.html

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Junqueyardjim
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1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

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Pull the cluster out, disassemble the three sections, then take a pencil eraser and 'erase' where the metal strip contacts the corresponding metal, then do the same for the opposite mating surface. A good electronic spray cleaner also works but the eraser is more thorough IMO.

Great idea! I'll check that out as soon as I remove the cluster.

thanks for the idea.

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1980 300SD (daily driver), 1981 300D (Inca Red)

Also check the fuse associated with the cluster. The same logic applies to the poor ground on the cluster. If the fuse is corroded/cracked/not clean then it may cause jumps in the current that show up as jumpy needles.

Make a ground strap from one of the cluster screws to the group of ground wires attached to the firewall frame.

X2

Establish a reliable ground and tie your components to it.