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More generator questions

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ChuckLuedtkeSEWI View Drop Down
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    Posted: 19 Mar 2010 at 9:45pm
Ok, thought my generator was shot.   took it out today after reading a few articles and learning some more on diagnosing it.   I read this article on YT forum.
 
 
I did the test between the F terminal and the brush that is connected to the field coils and it came out with a connection.  I also tested between the F terminal and the body of the generator to see if there was a short and nothing.  Also did a test on the A terminal and nothing, so that is all good.  As far as the armature, I look at the commutator bars and they looked good.  Mica material in between them is a hair down all the way around.  Also, tested from one commutator bar to each of the other ones, and got a connection between each and every one of them. 
 
After testing all these, I would think that the generator would be good, but when I tried to test it in the tractor running, there was nothing, unless for some reason I did not get a good connection for the ground and also the tester to see if it was drawing something.  
 
In the previous post, Butch(OH) and others told me to test the generator, with battery cables and see if it will motor.  Butch specifically says to do it one way with a negative ground and the other way for a positive ground so I don't get the polarity screwed up.  My question is after looking at the wiring diagram, my D17 should be positive ground, but I know that it is negative ground right now.  So which way should I test this generator?  Or is there a way to test the polarity of it first before testing the generator, to see if it will motor.   I know I could just take this thing to a generator shop, but I am trying to diagnose and learn.  You never learn something if you pay someone else to fix things.  Thanks for the help. 
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powertech84 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote powertech84 Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2010 at 9:51pm

Polarity shouldn't matter for testing, if you get it wrong you might have to re-polorize after your done. I haven't had the need to test many orange generators, but i do alot of green ones, they're all basically the same. I put the ground cable on the generator housing and the other cable on the field terminal and watch it spin. If it spins that way, but wont charge on the tractor, its most likely a regulator

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Brian Jasper co. Ia View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian Jasper co. Ia Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2010 at 10:22pm
Powertech is right about polarity. A generator doesn't care about polarity. Polarizing it is kind of like telling it which pole is ground. If you can make it motor, it's ok. The regulator usually does just 2 things. It has the cutout relay and the voltage regulator in it. Some of the larger capacity generators in automotive applications also had a current limiting function.
The YT article sends you out around Robin Hood's barn in testing a generator. You want to do the motor test by first running battery voltage in the "A" terminal and then ground the "F" terminal. If you run power in the A and ground directly through the F, you could have a shorted field and not know it because you wouldn't see the generator slow down when the field is grounded.
Without a "growler", you can't test the armature (part that spins) with the generator disassembled. An internally shorted armature shows up on the growler by holding a hacksaw blade over it and the blade will vibrate.
The regulator is fairly simple. The regulator has a coil of very fine wire wrapped around an iron core making an electromagnet. There are a set of points that are held in the closed position by a spring. The points make and break the ground path for the field circuit. As the voltage rises, the electromagnet gets stronger and opens the points. When the magnet gets weaker, the points close and the cycle repeats many times per second. In the automotive world we call that "duty cycle". The higher the duty cycle, the longer the circuit is closed. 100% would be on all the time. 50% would be on half the time and off the other half.
The cutout relay is simply an on off switch. If there were no cutout relay, when the engine stops, the battery would discharge through the generator. Remember the motoring test? The generator always has some residual magnetism and will generate a small amount of power. This is enough to energize an electromagnet under the cutout relay points and pull them closed so the generator can charge the battery.


Edited by Brian Jasper co. Ia - 19 Mar 2010 at 10:57pm
"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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ChuckLuedtkeSEWI View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChuckLuedtkeSEWI Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2010 at 10:24pm
I tried doing that tonite and it tried to spin but won't quite go.  I cleaned up the commutator bars really good with some fine sandpaper, but I did nothing to the brushes.  Do I have to clean the ends of those up or should I just put in some new ones to be safe.  I think I'm close on this thing, but so far away all at the same time.  
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Vinnie/S.D. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vinnie/S.D. Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2010 at 10:40pm
take a hack saw blade and clean the mica out too make it a little deepre too
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Brian Jasper co. Ia View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian Jasper co. Ia Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2010 at 11:02pm
The brushes are carbon and are fairly soft. I wouldn't go sanding on them. Like Vinnie says, make sure the mica that insulates the commutator bars from each other is not level, but below the top of the copper bars. Make sure the brush holder springs are able to put pressure on the brushes against the commutator.


Edited by Brian Jasper co. Ia - 19 Mar 2010 at 11:04pm
"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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Gerald J. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerald J. Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2010 at 11:00am
Showing no conductivity from A terminal is NOT GOOD. That should show continuity through the armature and brushes. My guess is that the brushes are worn to the point of not making contact or a flex wire on a brush is broken. There should be continuity from F to frame also, though it should be an ohm or two greater than the continuity from A to frame which should be a fraction of an ohm.

Gerald J.
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ChuckLuedtkeSEWI View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChuckLuedtkeSEWI Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2010 at 4:34pm

Ok, I took it all apart again, cleaned the mica out really good between the commutator bars, and installed a new set of brushes.  Same thing as before.  I tried to get it to motor up with a set of jumper cables and it spun a half of turn and that was it.  Same as before I put the brushes in.  So I am at a loss.  I guess it will have to go to the generator shop next week and get gone over as I can't figure it out. 



Edited by ChuckLuedtkeSEWI - 20 Mar 2010 at 4:35pm
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Brian Jasper co. Ia View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian Jasper co. Ia Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2010 at 4:39pm
Good eye Gerald, I missed that. No continuity between the A terminal and the frame is a problem.
"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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ChuckLuedtkeSEWI View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChuckLuedtkeSEWI Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2010 at 5:33pm
Ok, with it all assembled, I have continuity between the F terminal and the frame.  On my multimeter set at 2000, it reads out at 240.  Between the A terminal and the frame, I also have continuity but it is higher, around 400.   On a better note, I took off the generator on my HD3 and my WD which but are not rewired as of yet.  After testing both of those generators, they both motor well and are ok, although the WD generator, which is 6 volt could use some new brushes as the wires going to the brushes on one of them is really frayed, and was almost touching the frame.  At least I know those two are good and will probably just need a new regulator and cutout when I get that far. 
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Chalmersbob View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chalmersbob Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2010 at 6:36pm
Rememmber to polorize after installation. It may take more then one flash to get it polorized and to work. You can also flash it while the tractor is running. Bob
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Gerald J. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerald J. Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2010 at 7:53pm
Turning a half a turn and stopping hints at two opens in the armature winding or one opened connection to a commutator bar. You can confirm that by checking the resistance from A to case while turning the armature. It should vary a little depending on whether the brushes are centered on a bar or connection two bars, but it shouldn't go open. Yours acts like it will go open. If its bad solder at commutator bar its not a hard fix but you will probably disturb the bar and then need to turn the commutator. If its in the windings, its easier to find another than to rewind it but it IS possible to rewind it. Been there done that.

Gerald J.
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Steve in NJ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve in NJ Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2010 at 7:30am
Sorry Chuck, coming into this way late, but from reading your posts, sounds to me like a possible bad arm is the culprit here....
Steve@B&B
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ChuckLuedtkeSEWI View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChuckLuedtkeSEWI Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2010 at 8:09am

Thanks for the input everybody.  I will do the test with turning the armature and seeing if I find a dead spot.  Oh well, at least I tried.  I'll have to put a hunt on for another generator.  The one on my HD3 is the same body, but the pulley is different.  Maybe, I can swap the pulleys and put my HD3 one on for now to get it going and running and diagnose the rest of the electrical nightmare. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 49 WF Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2010 at 9:36am
I was wondering what chalmersbob is refering to when he is saying to polorize and flash the generator when the tractor is running.
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Gerald J. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerald J. Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2010 at 10:38am
Yah, if you don't polarize BEFORE starting and the polarity is backwards you close the cut out contacts with the generator ready to put out maximum amps backwards and you risk welding the contacts and burning out armature and brushes. NOT A GOOD SCENE!

Gerald J.
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