found my old vdo tacho in the boxes im unpacking from moving earlier this year but have not got the instructins... this is a 10yr old 52mm tacho that was the only gauge to survive from my mini.

tried to wire it up, as its only got 3 pins, - which would be ground, + wich would be ignition and the number 2 which im guessing would be the neg from the coil...

this produced no reading, but if i swap the - and 2 pin ires over it cuts power to the motor (must short the ign switch)...

how the hell do i wire this up? its got me baffled.

Is no 2 pin maybe light for the tacho and you just need to use - and + from the coil?

nah, lights seperate from the pins. the light globe has its own + and neg on the removeable light globe

well traced the ig wire, also found out that the pin marked 2 is the trigger wire and - was ground as suspeced (clarified this with auto elec before playing around... then tested the guage... it was shot!

Must have been that car accident 10 years ago... it read idle at 500rpm and by sounds 6000rpm was only 3000rpm (the tacho was for a 4cyl mini minor)... then it went hay wire and stoped working...
auto elec said wiring was correct but gauge was damaged previously, then i told him about the accident and he said that would do it