All Everyone,

I have just obtained a instrument cluster for my W123 (M102) 200, with a tachometer, my present one has only a large clock in its place.

Not being a electrical tech, I like to appeal to everyone out there for help in the tachometer connection. All I see is a pair of terminals labelled + and - and a separate terminal for the clock (I guess). I am wondering should the tach terminals be connected to the alternator 'field' coil or to the ignition coil?

All help and advice gratefully accepted.

Many Many thanks in advance!


Jimmy Ng
'82 W123 200

Hi again all,

Further to my post above, I have just browsed through the archives and it appears that the tachometer is either wired through the Diagnostic plug on the left fender of the car or by the flywheel (?)

I have checked through my car and it does have a black diagnostic plug. I would be thankful if anyone can advise me on which pins the tachometer terminals be connected to. Are there any other sensors that I have to buy to get the tachometer working?

Thanking all in advance.


Jimmy Ng
'82 W123 200