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Discussion Starter #1
My S/G starts my K341 no problem.
Gen light stays off at idle
Tach up the engine, Gen light comes on and stays on. (even if you back down to idle again).

I think the brushes are either worn, or not seated fully. What does everyone else think?
 

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I'd put a voltmeter on it to see what's really going on. Could be a regulator problem, or a grounding problem, too.
 

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Discussion Starter #4 (Edited)
Thanks to both, I cant get out and test gen and regulator for a day or two.
I'm guess I'm looking for scenarios that should be most evident and most likey the problem.
I am probably replacing the bronze bushing, because it's a little scored so I know I have to dissasemble (again). The brushes in there are from another generator. I got a used replacement for mine because front bearing went. But the used one's field coil was severly shorted so I used the meatiest brushes, the best end plate, the best armature, and the only working field coils.
bit of a frankenstien creation.
I recall after the first dissasembly of the frankenstein creation (due to the bronze bushing heating up enough to really burn my finger through the end plate) seeing the brushes were only contacting on maybe 20% of the face. Because the curvature was not the same. Voltage was between 12.5 and 14, I don't remember at idle. I should have checked at full RPM range. Got it all together, thought I was good to go. But throttle up gave me the Gen liht again. I shut it off, start again, lights off. RPM up, comes on.

So without access to test for a day or two I'm trying to zero in on likely culprits. Current thinking is that the brushes are jumping or bouncing on the armature when RPM's are increased.
Either way I'm replacing brushes because they were fairly worn, and the bushing could probably be replaced. That's two of the three parts of a rebuild, so I might as well replace the bearing or at least have a spare bearing on hand.

Wow, lot of words. Do I sound like less of a "shotgun parts at it fixer" at least? Given the new info (novel) what are everyones thoughts
 

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I'm always in favor of diagnosis before expenditure, but I'm retired (way more time than money).
Same here!

I have contoured new brushes to the armature by using very fine sandpaper, paper to the commutator, sand to the brush. Lightly press and turn the armature, the sandpaper will give the brush the same contour as the armature. Sandpaper is better than emery, as it's less likely to leave abrasive particles behind, as in the brush.
Put that shotgun down, Tex, and have a beer! :thThumbsU:trink39::thThumbsU
 

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Discussion Starter #6
Sandpaper between sounds like a brilliantly simple solution.
Thanks Fcub.

Shotgun down....beer up :thanku:
 

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You're welcome.
 

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By passing the regulator's control of the field circuit would either point a finger at the generator if the condition persisted, or eliminate it if the light on throttle-up disappeared. The difficulty there is whether your field circuit works off supplying power or ground. Delco was one way & Autolite was the opposite; I can't recall which was which (too many hours without sleep), & my old reference guides didn't make the move when I 'migrated'.
 

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Discussion Starter #9
Allright, got some wrenchtime,
from idle to 3/4 throttle generator puts out 12.5v,@ 3/4 throttle it drops to anywhere from 2v to 4v.
Throttle down from full throttle, voltage stays low.
If just above 3/4 when light comes on you can get it to go off sometimes but dropping the rpms again.
Turn off engine, restart same thing.

I'm still thinking its the brushes. Well I should have them, bearing and bushing tomorrow.

I'll let you know how it works once I get everything together.
 

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I agree, it looks like the brushes - maybe loosing contact with the commutator at speed. Are the springs still good? They should press the brushes fairly hard, even if the brushes are worn short.
 

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Discussion Starter #11
The springs are springing pretty well.
When the new brushes come in, I'll get 'em in and hopefully be up and running.

Thanks for stickin' with me through this
 

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My pleasure. Besides, I'm dying to know what fixes it!
 

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Discussion Starter #13
Got it working like a charm.
Well it was one of two things
1. the brushes
2. It just needed to be torn down, three main pieces painted, cleaned, bearing replaced and reassembled

I think it was the brushes, but it looks great now, a little awkward in the 37 year old engine bay...but it works!
 

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:congrats::congrats::congrats:
 
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