I followed the DIY on the tach for my '83 - 300CD Turbo, squinched the female plugs in the base, installed a washer in the cap and the TACH is now functioning.

Now my question is, are the following speed/rpm reading in the proper range?

60 mph = 2950 rpm
65 mph = 3100 rpm
70 mph = 3250 rpm

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1983 Mercedes 300CD Turbo- 199,370 miles - Lapis Blau
1974 Mercedes 240D - 186,445 miles - Aqua Blau
1982 Volvo 244GL Diesel wagon - 168,956 miles - to be sold
1994 Chevy G30 6.5 Diesel "short bus" converted for camping, painted red white & blue & white stars 78,956 miles
JD F935 diesel front mower

Sounds about right.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970