Tach Fix
 

I am looking at a '82 300D but the tach is not functioning. What might be the most likely problem. Also does anyone know what the revs should be at 60mph?

If its the same as my 87 190e then the tach's are electronic rather than cable operated. Check the lid of the fusebox, each fuse is listed, with the functions that it protects. On the 190 fuse 12 (i think) does the tach, engine cooling fan, and the idle valve.

Mark, I repaired my 1982 300D tach by re-soldering the circuit board on the sending unit located on the drivers side fender well under the hood. There is a detailed procedure in the archieves. Do a search and you should find it, if not, contact me and I will give you the procedure.

Tach Fix the Easy Way
 

Take the cap off the tach sending unit on the left wheel well. Seperate the cap from the sending unit. Might have to yank pretty hard.

Insert some metal washers the size of quarters in the cap. Reassemble the cap and sending unit.

Did this almost two years ago and it's still working.

The solder fix should be Plan B.

JV