Red wire is half wave DC. White wire is AC for the lights on the tractor side. There should be a diode in what looks like a fuse holder or a bump on the wire at the plug which is the diode. Those use red on the stator for DC and black for lights. If you have one with two black leads, it needs an external regulator rectifier. Two yellow wire on reg plug into the two black on the stator. Two black wires on reg plug into the tractor harness.