Slow5o

okay i have read posts on here and people say u hook the green wire of the autometer tach to the negetive to the coil now which one is the ground wire the yellow and green or the red and green

Portmaster

On all the Autometer Tachs Ive ever had it was green to coil neg, black to ground, red to the switched 12volt and white to the dash lights. Are you sure it's an Auto Meter?

projectresto83

green- (-)coil
red -12v switch
white- light power
black - ground
if there are any other wires such as ones that are looped back into the gauge then don't touch them. Some autometer tachs can be used on 4 and 6 cyl to have wires that get cut to get the right rpm read out.

Slow5o

its an autometer the 2 coil wires im asking which one is the negitive side of the coil yellow and green or red and green