Starter generator problems
 

I'm making a new thread after my previous one about putting an ammeter on my 70, i thought everything was running well but the problem has recurred.
This started after I rebuilt the starter generator and it started overheating. Enough that it started peeling paint on the bearing cover and its too hot to hold my hand on it.
After a ton of troubleshooting I thought it was fixed but its doing it again. To eliminate any other issues I disconnected the wires coming off the field winding and the small wire off the armature, just the heavy starter cable. It turns over the engine fine, plenty of starting torque.
After running for more than 20 seconds the generator body starts heating up.
I got an armature growler and it didnt show any shorts. I did turn down the commutator and polish it. The field coils seem fine with an ohmmeter, but could one of them have a short causing this?
Is my generator shot?

Could the bearings be bad?

They're brand new sealed bearings, they turn easily and don't make any sound.
the heat in coming from the body of the starter and the rear bearing mount plate.

Could be a grounding problem....

Didn't you say you were getting a new wiring harness? Is your tractor freshly painted that paint could act as an insulator between parts such as motor to frame, generator bracket to engine block, etc, etc. I would address that with the new wiring harness you are planning to install!

I hesitate to post this as it would be obvious, but is the armature showing signs
of rubbing on the pole shoes?
Another thought:
If you removed the regulator wire from the field terminal, then the Generator would not produce a charge as there is no excitation, unless the field STUD is no longer insulated and is grounded to the case where it comes through it,-------
Just something to check.
Also check the condition of the commutator for any signs of the brushes arcing,
as each segment should look the same compared to each other.
Also check to see that the armature windings where they are soldered to the commutator, have not been overheated and thrown/melted the solder out of the connections, that would indicate a bad armature.

Also check that your brush wires are not touching anything they shouldn't
like the through-bolts or touching the case.
Heat is either rotational friction or excessive electrical production/ground.
You mention installation of ammeter, did you wire it correctly?
They are not an voltmeter where one side is grounded!!
they are a "pass threw" as in cutting a wire and hooking each end to the ammeter terminals.:bigthink:
Edit:
I just looked at your profile, sorry,
I didn't know you were versed in electronics.

Wiring harness is in the mail... Not freshly painted probably a 15 yo paint job from a previous owner.
I broke down and bought another tested working unit and a parts one (has a broken ear bracket) from my parts guy (Bullpen Antiques in Canajoharie, NY) I will do minimal cleaning to that and put it on to hopefully get it running.
The grounding doesn't make sense as a problem because its getting hot as heck just sitting there spinning and unconnected from everything. In order to see if the issue was a bad regulator or wiring I disconnected all the wires from the generator except the heavy starting cable from the starting switch. So after the engine is started there is no current path to or from the armature or field terminals, unless there is an internal ground path that is intermittent?
The only other issue I can think is if I resurfaced the commutator down too far past the point where the brushes would bridge more than 2 sections and that is causing internal currents that is inducing heating?

Armature spins freely with no contact on the shoes
Yep ammeter connected properly, initially things were working and by grounding the field terminal could force it into charge mode and the engine reacted to load and the ammeter showed charging current.

See my above post, this all happened after I reconditioned the generator (new sealed bearings) and turned down the commutator. the new brushes I used sandpaper to make sure they matched well to the commutator and cleaned them off. I checked the Armature side brush to make sure it was well insulated, the ground side brush had a good ground. There wasn't much room for the brush connecting wires but with the insulating sleeving it looked like they where fine and weren't showing as grounded.

Is the FIELD terminal grounded?

With the unit running what is the voltage at the ARMATURE stud of the generator?

I'm also curious about all the wiring at the generator,
you said "To eliminate any other issues I disconnected the wires coming off the field winding and the small wire off the armature"
Did you goof, and mix up the FIELD and ARMATURE wiring?

What condition is the voltage regulator in, did you happen to open it up and see?

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Scratch all that, with the unit running and only the heavy ARMATURE wire connected it still gets hot.
Sounds like the FIELD is grounded internally.

Another silly question, is you starter /generator a type "A", or type "B"?

I will pull the generator off the tractor this afternoon and try to troubleshoot it.
when I reassembled it I checked all the connections with for shorts to ground and found none.
It was running at full speed with no electrical connections back to the regulator field or gen terminals and the case of the generator was quickly getting too hot to hold my hand on it.
I've looked over several of the delco manuals and don't know what type it is, I will right down the part number off the tag. This generator has worked on it for almost 2 years before i decided to rebuild it.

Replaced the wire harness that came in today, took off the generator and opened it up.
Commutator is really scored up from only an hour of use. When I cleaned and reconditioned it I polished it up with 600 grit and cleaned all the dust and grit out of it with a few shots of contact cleaner before I reassembled it. It was nice and shiney and smooth, now it looks really worn. Is that a sign of on of the coils being shorted?
The coils seem the correct resistance that I found in some over threads. Trying to measure any resistance to the case may be showing something that is bad? After cleaning the carbon and copper out my meter wasn't showing any path to ground, but now it briefly read 1 Mohm before going up to about 10 meg, so maybe there is an intermittent short when it warms up or jiggles, I started drilling the pole shoe screws out and will hopefully get those disassembled so it can unwrap the old insulation and see if there's any place that looks like it is shorting.
Armature still passes growler tests.