Originally Posted by renouji
which one is the tach wire? the battery or the coil? and how do i test it?
The bestiary to test is to pull the gauge or cluster to access he back of the tach. You should have a 12v wire (active with ignition on), a ground wire and a tach wire going to the negative side of the coil. If you have electronic ignition, the tach wire may go to the ignition module and not the coil. you'll need a multi-meter to check voltage with key in "on" position. You should look at a wiring diagram to track down the tach wire. Or check the color code of the wire coming out of the tach and follow it to the coil or module. You could check this wire for continuity with the multi meter. It may be cracked and shorting or bad connections.