Farmall Cub 3 brush generator rebuild problems

[seabeelt]

I’m sending the generator back now for the second time. When I took it apart there was no woodruff key at the shaft and pulley- disappointing. The brushes do not sit flush on the commutator they are the wire lead type - not flush is probably an issue I’m guessing. I’ve asked that the generator be thoroughly tested for motoring and voltage output as well as correcting any defects. We will see. I know 12v is an option but aside from the alternator kit you need to replace the battery and light bulbs but I’m trying to keep the tractor as original as possible. All that aside I should not be having to do this much work to have a generator rebuilt

[wil1bil]

Same problem, bench tested my generator off 52 Cub, ground to the body of generator(positive), jumper from F to the same ground point, then put the neg. to the A term. It runs. When I remove the jumper from the F term it stops. I watched a video that said it should go faster when the F jumper is removed. I have a 3 brush generator, not sure if the test was for a 3 or a 2 brush or if that even matters? Should it test the same?

[Gary Dotson]

Test procedure is the same. Here's the procedure: Case well grounded, connect the power source to the "A" terminal, the generator should motor in the proper direction of rotation (same way the engine turns) As it's humming right along, ground the "F" terminal. It should slow down significantly. When you are applying power to the field terminal (a bad idea, by the way) I'm guessing the rotation you're getting is reverse normal rotation.

[wil1bil]

Mine stops running when F is disconnected. Haven't checked the rotation yet.

[wil1bil]

Checked the rotation, generator running clockwise and tractor motor spins clockwise looking at both from the front of the tractor. Still will not spin unless I have a jumper from the F terminal to the positive ground to the generator body. Does this mean it's using the F to complete circuit and the other internal grd. from the other brush is bad so it won't run without the F? So jumper wire to F is the only way to get a complete circuit? Gonna go look at the brush and see if I can test with meter. Which brush is the question??

[Gary Dotson]

There are a few reasons why the Armature circuit is not participating. I don't remember which brush would be questionable, clean and check them all. If worm significantly, replace them. Clean (sand) the commutator portion of the armature very well, sometimes they're not as pristine as they look. Make sure the mica between the commutator bars is below the surface. Check the continuity from "A" stud to "F" stud, should be pretty low ohm value. Now we're getting to the armature, meter checks here are not conclusive, but it's a place to start. There should be full continuity between all commutator bars and none between the bars and any other surface of the armature. The only true test for a short is an armature growler. A starter generator shop would have one, if you need to go to that step. If you do these things and still no proper motoring, go back and spend more time on the brushes and commutator.

[Garyp2]

1950 Cub, not charging, pos ground 6v system. I rebuilt my generator including new armature, field coils, and brushes. I am not quite sure what the 3rd brush does? Of the 3 brushes 2 are insulated from the case. One of these goes to the A terminal on the generator the other brush to the Field terminal on the generator. The third brush is not insulated from case ground and there does not seem to be any adjustment? This generator is not charging and has an regulator not cut out switch mounted on it.