N Board Forum - Expanded Thread Page

Subject: Motor testing 2n generator

[Back] [Return to Top of Forum]

Steve Frysinger    Posted 10-21-2017 at 09:18:03 [URL] [DELETE]        [Reply] [Email]  
  • Motor testing 2n generator
  • Folks, I attempted to motor test a genny bought from Yesterday's Tractors. I freed the belt, removed the lead to the cut out, and ran a jumper from the negative battery terminal to the only stud on the rear of the genny. Not only didn't the generator move, but the jumper quickly overheated.

    So I assume I had this hooked up wrong, though it seems to match all the you tube videos and on-line descriptions I've seen. My next option will be to remove it and take it to a shop for testing, but I can't imagine a new genny would be at fault.

    Did I do something wrong in the motoring test?
    Thanks!
    Steve

    36 coupe    Posted 10-21-2017 at 11:26:39 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • Assume and imagine are words that should never be used in trouble shooting anything.Put the belt back on and start the engine.Look at the ammeter.Throw the jumper wire away.It probably 24 gauge china wire.For get the word polarize.

    Steve Frysinger    Posted 10-21-2017 at 11:45:52 [URL] [DELETE]        [Reply] [Email]  
  • Re: Motor testing 2n generator
  • I did put an old analog Sears engine tester on, and it showed a current, but in the opposite direction to the scale, so I couldn't read a value. Was that because of the positive grounded system Sears hadn't anticipated?

    Bottom line, system still isn't charging (no movement on tractor ammeter, no voltage change at battery with engine speed change).

    I have one more new cut out to install, in case something happened to the one I installed a week ago. Since I have a brand new battery and I know the wire between the genny and cut out is good, that's about the only other thing I can think of.

    Am I missing something else?
    Steve

    36 coupe    Posted 10-24-2017 at 15:19:18 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • Assuming again.Half the 6 volt cars in the 50s were positive ground.You have a meter but dont know how to use it.Find an old Motors Manual and study it.The cutout is a simple relay.The book will show you how it works.

    Steve Frysinger    Posted 10-24-2017 at 17:52:17 [URL] [DELETE]        [Reply] [Email]  
  • Re: Motor testing 2n generator
  • > Assuming again.Half the 6 volt cars in the 50s were positive ground.
    > You have a meter but dont know how to use it.

    Yes, I think you're assuming too much. I've owned several '40s and '50s vehicles, all 6v positive ground. But you missed the part about my multi-tester being from the late 1970s and designed for 12v negative ground systems. So the ammeter scale wasn't designed for this application. But it was enough deflection to show me current output, which seems inconsistent with my motoring test results. Talked to the local old Ford tractor mechanic about it today, and he agrees it's an anomaly and probably indicates a failed generator, but a bench test is planned.

    > Find an old Motors Manual and study it.The cutout is a simple relay.
    > The book will show you how it works.

    Thanks, but I know how the cutout works. And in any case the cutout was out of the circuit for both tests. I'm only asking this friendly group for tips with the strange results I'm getting.

    Steve

    36coupe    Posted 10-25-2017 at 04:49:42 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • Tell us how a cutout relay works.What happens if you wire it backward.

    Tony    Posted 10-21-2017 at 11:07:15 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • Good morning,

    My knowledge of 3 brush generator testing is limited but I know that there are two types of 3 brush generators, internally grounded and externally grounded. Since the field has to be grounded to motor a generator different procedures may be required to motor test each type of third brush generator. I have no experience trying to motor either.

    .....or it might be there is a short to ground inside the generator, Armature, field coils brush carriers etc. I had one years ago shorted from a washer left inside when it was rebuilt.

    Since the generator is new (or does new mean a year or so old but not installed?) from YT I'm sure they warranty them, don't they? Have you spoken with them?

    I doubt you damaged anything with the jumper wire unless you let the smoke out of 2 aught cable. 14 gauge wire heated below the melting point of the plastic insulation wouldn't have done any internal damage.

    At some point the generator will have to be disassembled and checked. Ain't no other solution IMO. Cocked brush, (usually the third) Shorted/open field, or armature.


    Tony


    Tony    Posted 10-21-2017 at 14:46:43 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • Hi Steve,

    The single lead is internally grounded. The field goes to ground inside the case.

    The externally grounded generators are the two wire A & F type. So.... I don't know how to motor test an internally grounded generator.

    I am curious if it can be motored and more important how the hell can I do it?

    Let us know what the shop finds is wrong with the unit. It's been a long journey.

    Tony

    JMOR    Posted 10-21-2017 at 17:45:36 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • You simply apply power between the terminal on rear and the housing. Power will go to both the armature & field coils (via 3rd brush).

    Steve Frysinger    Posted 10-24-2017 at 17:57:15 [URL] [DELETE]        [Reply] [Email]  
  • Re: Motor testing 2n generator
  • When I first tried to motor it I let the case ground to the engine (as it must do normally), but then I suspected a ground issue and connected the battery + to the case, with the same results. I might try that again though - I've tried so many configurations I might have set that up wrong.
    Thanks!
    Steve

    Tony    Posted 10-21-2017 at 22:52:22 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Motor testing 2n generator
  • Hot to terminal, ground the the housing. Of course, the case grounds the field. Simple.

    Arrrg! of course, the third brush completes the circuit. I should have known.

    TOny

    Steve Frysinger    Posted 10-21-2017 at 11:24:10 [URL] [DELETE]        [Reply] [Email]  
  • Re: Motor testing 2n generator
  • Hi Tony - thanks for your reply!

    Yes, you're right that I received the generator a year ago and just recently got around to unpacking the box and installing it.

    This is the first I've heard of two types of the 3 brush gens (which I gather I have - it's just got one connector stud on the outside). I can't imagine how else I could ground it apart from the case.

    Sounds like I'd better take it to a shop for them to test it... :(

    Thanks again!
    Steve

    [Back] [Return to Top of Forum]


    Top