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Old 10-04-2014, 03:29 PM   #1
Fred K-OR
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Default Testing Generator field coils??

Have a question about how to test the generator field coils to see if they are still good. I searched for specifics on this subject on this site and could not find any simple way(for me) to test. I am a little dense when it comes to electricity. Thanks
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Old 10-04-2014, 03:44 PM   #2
Joe K
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Default Re: Testing Generator field coils??

Continuity test (does electricity flow from one end to the other in the field wire.)
Short test (is there a flaw in the insulation between field and generator casing - done inversely to above as non-continuity using a Volt-ohm-meter)
Polarity test (Do the poles "line up" N-S correctly - can be determined with a compass - or is one or more poles "reversed" in winding or connection which causes one pole to counteract the other resulting in no generation.)

Tom may know of others...

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Old 10-04-2014, 03:50 PM   #3
Herb Concord Ca
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Default Re: Testing Generator field coils??

The 2 coils are wired in series. One coil lead connects to the ground brush, the other connects to an insulated brush. Disconnect both leads noting which one connects where. With a VOM set for resistance measure between the 2 coil leads, you should read a low value maybe 3-4 ohms. Then measure either lead to the generator housing this should be an open circuit.
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Old 10-04-2014, 04:55 PM   #4
Fred K-OR
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Default Re: Testing Generator field coils??

Thanks guys. I have tried some of Tom's ideas and things seemed to check out (if I did the tests correctly). But I will give your ideas a try also.

When I put the generator on a car and run the motor slow, it seems to generate maybe a volt or so taking the reading on the generator output. But when I rev the motor up, nothing shows on the amp meter. Guess one check I have not done was to check the output on the generator output when I rev the motor.

It also does motor when connected to 6 volt battery charger. I did put new brushed in this unit. Any other comments? (Take it easy on this illiterate electrical guy)
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Old 10-04-2014, 09:44 PM   #5
Drive Shaft Dave
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Default Re: Testing Generator field coils??

The one side of the field goes to ground. the other field wire goe to the insulated adjustable brush. The ground brush has a braided wire connected to ground. The output brush connect's to the output stud on the gen case.
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Old 10-05-2014, 07:50 PM   #6
Tom Wesenberg
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Default Re: Testing Generator field coils??

For testing field coils, I like to use a 6 amp battery charger with an ammeter. The more common long generator field windings should draw about 4 amps on 6 volts.

Clip the + cable to the ground end of the field and the - to the adjustable brush end. Lift the brush off the commutator, or remove the field wire during this test.
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Old 10-08-2014, 04:03 PM   #7
Fred K-OR
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Default Re: Testing Generator field coils??

Just though I would get back to everyone that helped me out on this problem to let you know what the problem was. As I mentioned above, I decided to take my generator to a fellow here locally that works on them and repairs them. What he found on the huckster generator was that the armature was shorted out plus a few other things that he took care of. Now it works great! Still don't know if the short in the armature blew the fuse or not but it could have. I had been running the generator a little high, about 10 amps, and did not use the lights much. Don't know but that may have lead to my problem.

He replace the coils in the coupe generator because long screws had been used to put the cutout on the generator (not by me, that was the way it was when I bought it) and they had bored into the coils. He also found a "bouncing" on the commutator. He found that when the commutator was ground in the past, the shaft ended up not in the center of the commutator (if that makes sense). Thus when running you could see the brushes "bounce". So he is going to true that up. So hope all problems are solved and thanks again for the help.

BTW is anyone wants to know who this fellow is, he is Tom Godish, 503-282-2212 located in Portland, OR.
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