Ok, so the alternator currently on the tractor has terminals labeled from left to right; E, S, L, B. S and B are the connector, with black wire going from S to L, and S having a red wire also going to B. B also has a yellow wire going to the starter solenoid, and a light green wire going to the voltage regulator. Terminal E has nothing connected and a dark green wire, that goes back to the voltage regulator, just dangling.
I do know the alternator is not currently charging, and the battery light is on. I don't want to make an assumption, but would the dark green wire just connect to terminal E?