Want to test this 67 factory tach and spec sheet says case in ground, Dark blue is 12V, Gray with trace is to coil - neg terminal. Pictures are front and back same orientation Which terminal is 12v, top stud or side tab.
I'm in the same boat ! do these look like the correct wires for the tach ?rt440magThe dark blue wire (12V) attaches to the long stud at the top, the spade is for the gray ignition wire coming from the coil negative.
Now on my fuse block , There is another blue wire coming out that has the same type push on stud connector . When does the blue wire need to power up ? RUN poss ?yes, grey wire to the spade connector on tach and other end through the firewall connects to negative terminal of coil. The blue wire goes to accessory side of the fuse box or ignition and provides +12 to long stud on tach.