Dear Tim;
Okay; Dist. primary is the one that connects to the side of the coil and then connects to the points/distrbutor (low voltage).
The wires that go in front of Tach's face plate are for the light.
The one that goes inside the Tach. may be (+) and the one leaving the light may be (-) using the light as a fuse (in series).
Please open up the unit & check the +/- connections to see if I guessed right etc....
Good luck, John M.....
