I recently acquired a 1985 300D. The cluster has a very strange issue in which any time an indicator lights turns on the temp and fuel gauges both instantly read high (the tach is broken so I don’t know if that would be affected as well). It gets worse with every indicator light that turns on.

One thing worth noting is that the backlight for the cluster and the turn signals do NOT cause this behavior. Also, whenever I turn on the brights the causes the seatbelt light to some on for a few seconds and the cluster buzzes at me.

I have already carefully redone the ground behind the cluster, sanding and coating each piece with dielectric grease. I have also redone the classis ground from the battery to the chassis. I have been unable to redo the ground strap between the trans and the chassis but it seems tight so I doubt it has a problem.

you did the grounds which attach to the steering column brace, or to the cluster, or both? any change at all when you did these? it would seem to be a gound somewhere. have you taken a gander at the tank sender and temp probes??

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

I ran a separate ground wire from the cluster to the under dash ground point on my 240D, fixed the jumpy gauge issue.

When i pulled the cluster out i saw 2 grounds, i cleaned both. Are there others?

You just attached it to the metal chassis of the cluster?

Yes, I just used one or the screws on the metal portion of the cluster and ran it directly to the ground point under the dash. I don't know what the real problem with the ground was, so I just bypassed it.

definitely worth a try!

You may have a bad trace on the circuit board. Had a customer with a 123 that had no gauge illumination even though all wiring was ok. Found a bad trace on the board & repaired it... all worked well after that. Check continuity from each pin at the plug to the offending light.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

I did this and it fixed the problem. The reading from my temp meter confirms it!

Glad to hear it worked.

I had a bad trace in my 1981 240d only one side of my instrament panel was illuminating so i took the board off and looked for burnt marks.. sure enough the trace on the positive side to the left bulb was burnt so i took my soldering iron and put a nice straight bead over it, works fine now.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.