2- Field Wire Alternator: Blue/Green wire hookup

When you look at a rotor, you can see the "fingers" of the end cores which wraps around the edges. the rotor is a simple solenoid coil electromagnet, and the "fingers" wrapped around from each end form the north/ south poles which alternate. Of course when turned, the engine adds the power, the rotor moves and you have a "moving alternating electric field." The blue wire provides full battery power to either end, and the green VR wire controls "the amount of ground return" IE the amount of current flowing in the rotor. More rotor current, = more alternator output. The VOLTAGE the alternator outputs is dependent on the load on the system, and the VR senses that voltage and constantly adjusts rotor current to keep the output voltage correct. The VR MUST be grounded exactly to battery ground potential, and the VR IGN terminal MUST be exactly same potential (no voltage drop) to the battery positive.