i need help getting my tack to work. i recently installed a 1984 turbo diesel engine from a w123 in a 1980 euro 280c 4spd manual. everything works great except the tach. i have the 280c tach in the car but still have the 300d as a backup.
i cant find any wiring diagrams. the 'tach/diagnostic' plug unit on the drivers firewall appears to be the same. i dont have any m110 engine wiring so i dont know what was. i wired the sending unit at the flywheel directly to the tach but nothing. i put the speed sending unit on the back of the 280c speedo but took it off because it made the speedo irratic.

thanks don

tacha amplifier on the right-side fender wall. Do a search for cigarette butt and tach and you'll see what I mean for a possible fix. It's round and has a cap on it that turns off.
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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want-- the '80 280c and the '84dt don't use this unit.
thanks

don