Rep Power: 0

Okay I bought an autogage carbon fiber tach and I took it to a shop to get it installed. However they said it's faulty and doesn't work. They said it flashes when they turn on the car but then shuts off. So later I when I'm home I test some things. I turned the key all the way so that everything is on but the engine and the tach lights up and stays on! Once I turn the engine on however, the tach shuts off. Then I opened up my hood and I didn't even see the green wire going to the ignition coil and I didn't a grounded wire. Is my tach faulty or did they just screw up wiring?

 
Rep Power: 0

The grounded wire can be anywhere along the metal part of the frame, so that wire can be anywhere other than the engine bay, but about the light on the tach could be because of the dimmer switch wire, then about your pickup wire it could be on the wrong side of the coil. but when you bought the tach it should of came with a different way of picking up a signal i think that wire is brown or something, but i used that wire on my car and its a whole lot easier for me but it only works on cars that are fuel injected.