I recently bought a 1993 300D (had an '83 & '84 before), and the tach and cruise control both don't work. I have rebuilt the fuse box and replaced the over/volt relay with no results. I have read the cigarette butt posts, but don't see the cylinder mentioned in those posts, and suspect the system has changed from the mid '80 models. The tach and cruise control both get their power through the same fuse, and I am wondering if there is a common connector that often fails? Thanks for any help.

Try swapping the fuse for a new one. They are cheap and sometimes do need replacing after 9 + years.

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Jim

Thanks for your suggestion. I have already replaced the fuse in the fusebox in the engine compartment on the driver's side, with no change, and all the other components that feed through that fuse are working fine, except for the tach and cruise control. Is there another fuse I am missing?

I have an almost 100% sure solution for this problem.

This is beacause I had the exact same problem a while ago.

The cause is a lost ground connection on the instrument cluster and I fixed it by simply connecting a new ground wire directly to the back of the cluster.

I'll go out and check the exact position I used because I can't remeber exactly where I put it.

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/Per

MB E300TDT -98

Please do let me know where you put the ground wire. That would be great if that fixes the problem, and I will sure let you know.

I ran an additional ground wire from the back of the tach metal housing to the frame, but it did not solve the problem. The clock in the tach assembly works fine, so I have power and ground (at least for the clock). Is there any way to tell if the tach is receiving a signal, and do the tach and cruise control in any way work together or depend on each other?