ibought a tachometer off a freind and i was wondering how to hook it up. it has 4 wires...a red, black, white and green one. the red and the white are both power wires, red being the main power and white being the back lights. the black is obviously the ground, and the green is the big boss out of the 4. im prety sure i can get them all hooked up aside from the green, reason being is that i have no idea where to attach it. the friend who i bought it off said something about wireing it up to the main harness or some **** but he wasnt to sure.

can anyone help me out with the green? btw my truck is a 95, xl, 4x4.

 

Coil negative.