Farmall Cub 3 brush generator rebuild problems

[seabeelt]

Hi Folks. Reconstituting this thread I’m having the same issue as the original poster. First let me lay the ground work. I have used the trouble shooting flow diagram and end up at the generator is bad box. Second, the generator has been serviced by a reputable vender often mentioned here on the forum and sent back once already. The generator motors (what I would consider slowly) with the field grounded but not otherwise. There are multiple versions of YouTube videos and internal connection diagrams about 3 brush generators ( not that you should believe everything you see and hear). However there is more than one source that says that the generator should motor (faster) with only ground and the A terminal connected and then slow down with the F terminal connected. ( not that you want to let it run much without the F terminal connected) one source is yesterday’s tractor ( which shows a different wiring diagram than what Jim describes) Soooooo. Which is truly correct??? Because as internally connected as Jim describes the generator ONLY motors with the F terminal and case grounded and hot applied to the A terminal AND I get zero voltage output from the generator AND I have good grounds AND I have done all the tests on the Flow chart diagram AND the light switch operates as it should... I’m stumped. Thus is a simple circuit and should not be this difficult.....

[Gary Dotson]

My method: Case grounded, apply power to the A terminal, the generator should motor along nicely, now while motoring, ground the F terminal, motoring should slow down but continue motoring. If it does not perform this way, there is a problem.

[seabeelt]

Hi Gary. Yes I have a problem. My Generator definitely doesn’t motor with only the case grounded and power applied to the A terminal. It only will motor if I ground the case AND the F terminal with power to the A terminal. The vendor says this is normal. I can fix anything but I need to know what to fix. Any ideas???

[Gary Dotson]

I would find a more reliable vender!

[seabeelt]

I would but need to get this resolved first

[seabeelt]

Any one have any thoughts as to “why” it only motors with the F and ground grounded and power to the A terminal when it should motor with the case grounded and power to the A terminal?

[seabeelt]

Question. Should the iron blocks that hold the field windings in place be magnets or be magnetic? Mine have zero magnetism. Won’t even pick up a paper clip

[seabeelt]

If magnets how does one re magnetize them?

Center windings on the armature all read 0.2ohms on the lowest scale on my meter. Research says this is normal for the 180 degree opposite however the adjacent side by side should be higher It doesn’t matter where I put the test leads from the meter. They all say 0.2 ohms

No shorts found between the A post and the case or between the F post and the case

Field windings read 2.4 ohms

[Gary Dotson]

No, the pole shoes are not magnets. Your observations on the armature values are what I often observe. The problem is that you can't fully test an armature without using a growler. I've been wanting one of those for a long time, so I hit ebay again, looking for a reasonable price. I've got one on the way, of course it may be junk when it gets here, seller says it hasn't been used since the 80's. I was checking a generator that I had on the shelf, I thought it was a good one! Turns out, it acts just like yours! Only motors very slowly, backward, when power is applied to the field post. No action on Arm. I can find nothing wrong with it so I can only guess that the armature will fail the growler test. There have been a dozen times, at Cubfests, that I've run into this and wished I had a growler to confirm diagnosis.

[seabeelt]

Thanks Gary. I’m going to send it back one last time this week Do you know of a source to get a new non rebuilt one?

[Eugene]

If the shop can not solve you generator problem, consider replacing it with an alternator. Much less expensive than some of the remanufactured 6 V. generators on the internet.

[Gary Dotson]

The mail lady delivered my growler yesterday. As the seller mentioned, it needed a little re-wiring, which I did. It works as good as it ever did! It showed my armature to have no problem and led me to dig farther to find the problem. Turned out, it was nothing more than a ground brush that was stubborn about making good contact with the armature. I'll have a working generator available at the next Cubfest.

[Jim Becker]

. . . Turned out, it was nothing more than a ground brush that was stubborn about making good contact with the armature. . . .

That reminds me, one of my dad's standard practices when a generator acted up was to give each brush's spring arm a little snap.

[Glen]

Hi,
When replacing brushes in the Cub 6 volt starter, I leave the screws that hold the brushes on slightly loose when putting the starter together, until it is fully assembled.
This lets the brush turn so it can make full contact on the commutator. The springs will hold the brushes down on the commutator. Then tighten the brush screws through the holes in the case.

I think you can do this on the 6 volt generator too, but I don't remember if you can get to the screw heads through the holes in the case. Maybe someone that has a generator off a Cub could look at it.

[Gary Dotson]

There are a couple different styles, Glen. My brush's are the attached lead style, no screw through the brush. On the type you speak of, yes they can (and should) be tightened post assembly.