I bought a shift light off ebay and use my stock tach but u set it on the back of it. There is 3 wires and I dont know exactly where the 3rd one goes if someone can tell me off the bat that would be great and what wire to splice into on the stock tach.

Red is 12v ignition switch
black is ground
and green goes to either a coil blaster or msd unit which i dont have either and would like to know if its possible to hook it to a certain wire on the back of the stock tach and which wire. TIA-John

 

yes it should be a blue wire

 

thanks, I see a solid blue wire with 2 silver circle spots the last wire on the driver side and I see a blue/yellow wire in the middle???