The green wire should be the ignition(-). Do not confuse it with the regular ground.
Check your manual where to find your diagnostic connector( the one they put a jumper on for smog check, and where the diagnostic codes are checked); it is usually in the engine compartment, or maybe under the steering wheel.It is usually covered by a cap that says DIAGNOSTIC. Somewhere in or around it there should be the IGN- hookup.
Some other possibility would be to check for the ignition- cable coming out of the distributor(that is if you have a distributor).
My 91 Toyota has both, but I hooked my tach to the IGN- right besides the diagnostic connector in the engine compartment.
WARNING; my tachometer says that when the tachometer is hooked up, never let the tachometer ground itself( it means it should never touch the chassis or any metal, and also that the cables going to the tach should be VERY WELL SHIELDED!!); otherwise it would ruin the coil of your car.
That also means be careful with the cable not getting frayed or where you place the screws if you hook the tach to the chassis.I would recommend hooking it to a plastic part of the console, or place it over a rug or rubber glove so that the tach does not touch ground(chassis).
The green wire is supposed to go to the negative wire of the coil , that is usually a white wire, but make sure that the tachometer documents tell you to use the negative wire it is usually the white wire. If you have a test light hook the cramp to the negative of the battery and check the two wires if the light glows that is the positive, connect the green wire to the other wire it will be the negative. There are some that say to use the positive, ""PLEASE READ THE INSTRUCTION VERY CAREFULLY"" Or you could short out the coil and the igition module.
ok. the first thing u do is unplug the ignition coil and find a red and black wire and just kinda skin it and touch it when the car is on to see any movement and the dimmer switch pull it out and find a green and blackwire hook the white wire up to that and test the lights you know turn the head lights on everything else is instructions when you buy the tach.