Farmall B ignition

My current problem is a new one. The battery was charged today and load tested OK at the battery place. Installed on the tractor and the starter will barely turn one revolution. Sometimes it won't even turn over at all. Just moves the fan about an inch and quits. What are the chances my starter suddenly went south on me? I am going to put the battery on charge again just to be sure it is full and will retry tomorrow. How would I ever know if the starter was good or bad? Scare up another battery and try it? Seems like so much going wrong at once that I end up chasing my tail.

What is your negative grounded to? Being 12v, I'm assuming the battery is larger than a 6v and therefore not in a battery box, so I'd wonder where it's located.

I think the factory ground was to one of the bolts holding the tramsmission cover down. I've also seen them grounded to the smaller of the two bolts hanchoring your steering support. Either should be a good ground as longs you've got a clean connection.

Have you been hooking and unhooking your cables (especially the ground) a lot while tinkering with the alternator? And (again, I know NOTHING about alternators) but wonder if the diode or resistor you wired into her is doing its job, and that the battery isn't draining through the alternator, if that's even possible.

I'd drive my truck/car up beside it and hook up the leads to the tractor battery and try to jump it. If it jumps then it's the battery, if not the it's wiring or the starter.

Check your battery terminals for corrosion. sometimes they corrode inside where you can't see them. Your battery cables and starter switch might be crapping out too?

Have ou checked the condition of the brushes on your starter? You may not be getting a good contact?