hey yall, I was just curious...I just picked up an autometer 5" tach with the memory function and there are four wires. red, Black, White,Green, what are the 4 wires for....red and black im guessing would be power and ground, and the green for the tach signal, what is the white wire for, I bought it out of a race car at a junk yard...so I dont have hte instructions? plzz help