Old VDO tach

[56rag1914cc]

I found this tach in my attic and want to hook her up. I can see on far left (backside) it says 12 v but the other two connections Im not sure of. I know one should go to neg side of coil and one ground but does anyone know which one is which?

[Marc]

Can you make out any markings on the two "mystery" terminals? Looking for "1" or "G", "-" or "31".

If not, use an ohmmeter to check for continuity from the body of the tach to each terminal. The one with the lowest resistance would be ground, the other one goes to Term 1 (the "points" side) of the coil.

[56rag1914cc]

Ill look when i get back home. I guess worse case i hook the ground up wrong ill find out when the tach doesnt work then just switch the wires up!

[56rag1914cc]

The needle moves but not with the engine rpm!