Farmall Cub

The battery on our Farmall 100 regularly goes dead. Usually I jump start it and it runs OK. Recently, it stopped running after a a few minutes. I would jump it again, and it would run fine a few minutes and stop. Any ideas? The engine was recently overhauled, and I suspect that the generator is not charging properly -- the ammeter shows a discharge, although I don't know how reliable it is. Should I just go ahead and replace it, along with the regulator? The generator is probably the original. Or if not, it's at least 40 years old.

First thing to do is polarize the generator. Ddo this with engine not running take a short piece of wire and momentarily jump from the bat term to the gen term of the regulator. Do NOt jump to the field. If that does not solve it try this trouble shooting chart.

diagram compliments of Farmall Bob.

Thanks. I studied polarity yesterday, and that could well be the problem, since I disconnected the positive lead on the battery the last time I used the tractor. (Although I've done that before without this happening.)

I'm kind of leaning toward just replacing the generator & regulator and be done with it, since these parts are so old.
Very glad to have found this forum, as my mechanical knowledge is pretty limited.

Since the tractor ran fine after being jumped -- for a few minutes -- and the ammeter showed a discharge, I'm thinking the problem has to be the charging system. Does that seem right?

yes it does.

Your biggest problem right now is that the tractor will not run with a flat dead battery. Right now it's only running on the brief charge it's getting from the jump start.

Put the battery on the charger overnight, up to 24 hours even, and it will start and run like it should. Then you can tackle the generator/regulator problem.

Look up "JohnT generator troubleshooting procedure" on google. It's a simple, succinct process for figuring out exactly what's wrong, and what exactly needs replacing. Unless you have $$$ to burn, and want to waste it on the "parts shotgun" method of fixing the problem....

The new generator & regulator seem to be working, but now I have a problem with the fan assembly, which I discovered after several hours of mowing. It seems to be wobbling on its shaft, and the metal around the generator pulley is beginning to shred. Did I maybe have the belt too tight? It looks as though I will need to replace it, although that sure is a tight space to have to work in.

I will attach a photo as soon as I figure out how.

this is the fan assembly.

Yep....looks like you're gonna have to get in there and replace it. Easiest when you take the front nose piece (grill housing) off, then remove the radiator. Take about 10 minutes to get to.

Is there anything else I should be on the lookout for when I do this? It feels like I've started pulling on a thread that is going to keep on unraveling. And I am no mechanic.