The tach on my '82 works perfectly for the first few minutes on a cool morning, then begins to jump around, and then quits altogether. The rest of the time it does not work at all. I can't find anything in Haynes about tachs (never can find the particular thing I want in Haynes!)How is the tach activated in a deisel? -- obviously it does not run off the ignition system. Anyone know what might be causing my problem?

Andy,

It sounds like your tach sending unit is heading south. You should do a search in the tech help and diesel sections, this topic is very popular among diesel owners. The sending unit gets a signal via a sensor that is mounted at the front of the engine near the crankshaft pulley. Its a grey wire that goes to the sending unit. From there, I believe it goes to the tach. It's a pretty simple set up.

SW

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2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
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'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold

Andy,
I had the same problem with my 1982 300D. Repaired the solder connections on the small round printed circuit board as per the instructions in a thread on this site. I think you can find it by doing a search.
Is your last name the same as mine?

Good luck,
Richard Seaman

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Richard Seaman
1982 300D Turbo 198k
1987 420SEL Sold
1993 400SEL 123k
MBCA Desert Stars

Thanks for your help, guys. Not being a smoker, I put a small rubber gromet under the sender unit cap instead of a butt, screwed it down firm, and presto -- tach works like a dream.