Tacho not working on '75 260Z

Well along with many other little quirks my new Z has, the Tacho doesnt work... not that I really need it because its Auto but I would rather it work.

So basically it doesnt work... BUT sometimes when I turn the ignition on or turn the R indicator on, it flinches. The needle will move a tiny bit or go right the way around and back really quickly.

I have the wireing diagram from a official Nissan service book(came with the car). I pulled it out(tacho), had a look and a wiggle of all the wires but no good. Neer the coil though, there is a dark blue wire that looks to have broken off something. its hanging loose and has a black rubber connecter or something on it! It goes into the main loom.

Thanks for the help :laugh: