Tachometer

Cable.

The tach is NOT cable driven on a 300DT. The tach gets its signal from the pickup at the harmonic balancer. The grey harness goes up to the diagnostic plug on the inner left fender. The cap is a electronic circuit board that converts the A/C signal to the signal the tach understands. Unscrew the cap, remove it, look at the pins, reinstall the cap. It may start working right..... It was a very poor system. In the 84 year models and up, MB got smart and put the tach pickup on the flywheel. Much better system.

harness goes up to the

board that converts the

look at the pins,

If it doesn't, try putting a cigarette filter in there. Works for me. But only for awhile then I have to replace the cigarette filter. Been meaning to try a pencil eraser.

the tach pickup on the