Hi I'm having trouble trying to troubleshoot my tachometer wiring I cannot find any tachometer wiring diagram if anyone has one it would be greatly appreciated. The tachometer it's self is working great but when I have it hooked up in and the engine on the needle jumps around so I tested the connector pins to see if I could find ground,power and signal. It's a 6 pin connector but only 4 of them have pins. So I tested for power and continuity on the pins. I found a black/blue wire that has 12-13 volts which goes to pin 15/54 on the rpm gauge I'm pretty sure that's the ignition wire it doesn't fluctuate when I presume the gas. Then I traced two brown wires that go into one pin together to a cluster of brown wires that are grounded to the frame. After that there are two more pins one has two grey/blue wires together that have no voltage but I believe to go to the lights and the last one is what I think to be the signal wire but I could be wrong it's a green/black wire that when I tested for continuity it was blank. So I popped the hood and noticed a green/black wire disconnected from something laying next to the ignition coil I attached it to a ground and tested again for continuity and it beeped. So I'm not receiving any signal voltage and this green/black wire is just laying next to the ignition coil negative side so I then tested negative side of ignitioncoil while I pressed on the gas when it was idlenit was at about 8 volts then when I press gas it jumped way high. So I got really ballsy and attached the loose green /black wire to the negative of the ignition coil hoping it would be the signal. But the car wouldn't start and sounded like craps when I did. So I disconnected it. No damage occurred. Still stumped though. And its obvious someone disconnected this green/black wire for a reason.