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  1. #1
    New Member Greg_Thomas's Avatar
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    Mar 2006
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    Charlottesville, VA
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    Mahindra 4110

    Default diesel won't charge battery

    I have a Mitsubishi 40 HP diesel dozer that stopped charing the battery. I replaced the alternator and belt, then the batteries, (24v) and it has worked fine for 6 months since then. When the batteries are charged, it starts like a new engine- first try. That is, until last Saturday when it wouldn't start again.

    As I recall, when I first had this problem someone here said, I think, that the alternator can get polarized wrong (or something like that) if the power is cut off while th engine is still running. This dozer has a electrical power switch which I may have turned off too early.

    Anyone have any ideas?

    Thanks,
    Greg

    Alternator is is A1T70783 2116 34468-26100 24v 20a
    with heavy white wire , and plug w white-red stripe, white
    Greg Thomas

    _______________
    Mahindra 4110
    Mitsubishi MT160
    Mitsubishi BD2G
    Cat 301.6

  2. #2
    Epic Contributor Soundguy's Avatar
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: diesel won't charge battery

    Make up your mind.. does it have a DC generator ( that can be polarized to different poalrities ).. or does it have an alternator.

    Most alternators on modern equipment have internal regulators. Gennies use external regulators like some older alternators.

    Once you decide what you have, post back.

    soundguy

  3. #3
    New Member Greg_Thomas's Avatar
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    Mar 2006
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    Charlottesville, VA
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    Mahindra 4110

    Default Re: diesel won't charge battery

    It is an alternator.
    Greg Thomas

    _______________
    Mahindra 4110
    Mitsubishi MT160
    Mitsubishi BD2G
    Cat 301.6

  4. #4
    Bronze Member
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    Mar 2006
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    TX

    Default Re: diesel won't charge battery

    An alternator has to be "excited" to charge. There should be one wire going to the alternator that is "hot" with 12v at all times. Many times when people think the alternator is bad, it is not the alternator, but that it is not being "fed" 12v to excite it. With the key on, but without the engine running, check the wires going to the atlernator, one should show 12v. If you don't find a hot wire, trace them down to see where they originate, and see it there are bad connections, etc. to find where you should be getting a 12v feed.

  5. #5
    Epic Contributor Soundguy's Avatar
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: diesel won't charge battery

    Birdman.. be a little more specific. You are likely refering to a common delco 10/12SI style alternator.. a '3-wire' job.

    It has a charge lug, a sense lug, marked as #2, and an excite/field lug marked as #1.

    The #2 lug can be loope ddown to the charge lug. ( thus can be always hot. ).. This lug's sole purpose is to monitor charge votls at the battery in case the internal regulator needs to pump up the voltage due to voltage drop across an automobiles many dozens of feet of wire harness... this wire would go right to the battery in many applications.. for a tractor with a few feet of wire harness.. this wire can loop tot he charge stud.

    The #1 line is the excite line and it needs to be switched.. IE.. on one when running.. or it will le tthe battery drain down. If this is on a gas engine with battery ignition, and you are feeding the excite line from the ignition line.. you need to add in an idiot lamp ( 194 bulb ).. or a diode for isolation. Even if this is a diesel.. the diode is good protection for the alternator in case the charge line ever comes un done, as the alt can try to charge out of the #1 line and cook the regulator unit.

    soundguy

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