hey guys, i just bought a tach, and the green wire is supposed to connect to the switched power wire from the back of the gauge cluster, right? i connected it to that and the red wire to 12 v source and the black to ground, and the tach still doesnt read my rpms, what could be wrong?

 

Take out your multimeter and check for activity on the green line you spliced. If there is activitity check your ground wire. If that works then try another guage.

 

i dont know what tach you have but the green wire is the rpm signal on mine,,and i tapped into the blue wire at the gauge cluster..

then the black is ground,white is illumination and the red is power..

 

What kind of tach is it. Autometer tachs have wires in the back you have to cut to convert it to 4 cylinder.

 

its a sunpro 3 1/2" powerline tach, it has switches on the back for cylinder, does anyone have a pic or mroe details of the wire your supposed to splice into? i spliced into the hot one with the engine running (yellow and blue) and its still not working, but when i am running my car, the tach is still bouncing around, so obviously i've cut the wrong one