Have a 1984 190D with 2.2 engine and 5 speed trans. Tach was working fine, then started working erractically. Quit working completely now. Any troubleshooting ideas ?

Thanks

Corroded connection in the circuit more than likely.

I had exactly the same problem. I pulled the sensor from the bell housing and cleaned it, then went to the connector behind the battery and did the same for the Klima relay on the firewall in the same area. Don't know where the problem was but after cleaning all and firing it up, it's been working perfectly the last 4 weeks and 1000 miles.

Another guy with the same car claims the solder joints on the board in his Klima were crystallized and resoldering them cured his problem. I didn't have to go quite that far but that was going to be my next step.

Thanks for the advice. I figured it was something like that.