Greg, for my exciter wire I took a wire from the ignition switch to a small light bulb then to the alt. Turn key to on the light powers up, when you start the car the light goes off---works the same as an idiot light. I used a 42 amp alt and my gauge reads to 50 amps, that way you can`t overload the gauge and cause a fire. Another point, just recently my gauge went bad and it took out the diode in the alt. I fixed the alt and put both wires on the gauge to one post to complete the circut---turned the set up in to the idiot light system. I will convert the gauge later to a volt meter---more reliable. I thought if you use a two wire alt you have to have an exciter wire?? Good Luck.....Lee: