OK- I'm gonna provide the information given to me by my 86 year-old father over the phone: He has a 1950 A-C B, that he had converted to a 12 volt. After 10-15 minutes of running, it would shut down, and not restart for several minutes. Someone told him that the 12 volt conversion was overheating the electrical system,and that he needed to put a resistor in, and that person put one in, and the tractor has not started since.It cranks, but won't turn over. I live 3 hours away from my dad, and I am determined to get this thing running for him while I still have him in my life. I have never worked on a tractor, and I don't even know where the resistor would be put in the electrical system. If anyone could give me any advice on where to start my quest to fix his tractor, it would be greatly appreciated. I have replaced starters, alternators, distributors,etc, on cars and trucks, so I do have a basic understanding of how to identify these parts. Help!!