IH Farmall 656 gas/ IH 240 Utility/ 2, Super C Farmalls/ 2, Farmall A's/ Farmall BN/McCormick-Deering OS-6/McCormick-Deering O-4/ '36 Farmall F-12/ 480 Case hoe. '65 Ford 2000 3 cyl., 4 spd. w/3 spd Aux. Trans
Is it possibly the wire that goes on the connection marked BAT (for battery)..?? If this is the case, if you trace the wire back, it should go back to the ammeter. Current flows through the ammeter, then through a wire to the starter switch battery post, so as to charge the battery. So basically a direct link to the hot side of the battery.
If the connector has come off the end of the wire, crimp a new one on, and reconnect to that post on the regulator, and your charging problem may be solved.