I have a rally tach for my 65 GTO and am stuck on the wiring. It's the kind with two terminals. One has an "+" and the other one is unmarked. Does one side go to the neg coil side and the other the battery side? Thats how it is now and the gage doesnt work. When I turn the key in the on position the tach just flings forwards and comes right back to zero and stays there. Please help.