I've got some hawk brand tach that I bought at a garage sale. I'm trying to install it on my daily driver Jeep I've got 5 wires red, black, yellow, green and Blue. The blue is slightly bigger gauge. can anyone help me figure out which wire is what?

 

black should be ground, red positive from ignition, blue probably negative on coil, green or yellow is hooked to the headlight switch, and the extra wire(green or yellow depending on which was left over) probably has something to do with how many cilinders the motor has. but not sure.

 

i've installed 3 tachs, and i agree for the most part. black is ground, red is power. but i remember green being for the neg. ignition coil. yellow is probably for lighting. if blue goes to the neg. side, i don't see why it needs to be thicker wire... perhaps you should just hook it up loosely to test it out.