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...but then later me and my friend took a look at what they did and they didn't even ground the wire and they didn't bring the green wire through to the ignition coil!!!! They only hooked up the 12v one so the tach will work and I can change the settings when the car isn't on but I have the keyed turned to the farthest point before the engine comes on. When I do that the tach light comes on, but when I start the engine the tach shuts off. The tach is fine right? They screwed up with the wires correct?