Electrical issue, High voltage

Discussion in 'Electrical Systems' started by wiseryder, Oct 21, 2017.

  1. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

    1,887
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    Sep 11, 2004
    belding,mi USA
    Hi everyone, I cleaned my car last nite, went to take it out today , dead battery.
    I think I must of left door open a bit and dome light drained it.
    I charged it, got it running, took it for a ride, voltage reading about 17-18 volts
    I have never had a problem with this car in 10 years until now
    Battery is in trunk, when I got home , I could smell something.Pulled battery cover off .
    It and the battery are super hot, I have no clue what happened, Like I said , never any problems before ...
    any ideas? . Im lucky the battery didn't blow up ....
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    Apr 14, 1999
    Bismarck, North Dakota
    Did you check it with a digital voltmeter? If it is 18 volts with a digital voltmeter, that says the alternator is not being regulated. You can pull the alternator and have it checked out, of you can simply replace the regulator inside the alternator (if you have an internally regulated alternator), or the external regulator if you have that style. Usually the regulator is the problem with high voltage.
     
  3. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

    1,887
    10
    Sep 11, 2004
    belding,mi USA
    Gary, I have autometer gauges and a Fitech system, the Fitech handheld shows voltage and it's way high
    I will check it tonight tho with a meter,
    What ya suppose happen to it all a sudden, never had this happen before?
     
  4. Twisted_Metal

    Twisted_Metal Moderator Staff Member Lifetime Gold Member

    25,260
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    Feb 26, 2004
    Bloomington, MN
    I bought a new alternator which had a defective regulator... It pegged the gauge and toasted the ignition module within seconds of starting the engine.
    (Ignition modules won't tolerate unregulated voltage.)

    I took it back.. They said it tested good. But they couldn't tell me the voltage it was putting out. :screwup:
    They replaced it with a different one AND gave me a new ignition module. No problems since.

    Most auto parts stores still carry rebuild kits for our style alternators... $15 or so.
    That's where I would start in your situation.
     
  5. SRGN

    SRGN Veteran Member

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    Feb 20, 2009
    Central NJ
    See why the alternator is putting put so much voltage. Could be a bad alternator/regulator as stated above, but could also be a poor connection. If the regulator is reading lower voltage at the post, it will try to raise the voltage to compensate. The dead battery that started the whole debacle may be the best place to start. Look for a parasitic draw, if the regulator is "stuck" it will allow current to flow through it even with the car off. Diagnose before buying anything. Charge the battery out of the car and test it.
     
  6. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

    1,887
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    Sep 11, 2004
    belding,mi USA
    well, absolutely nothing is loose, no wiring, nothing.
    Its an internal kind of Alternator, car has been sitting for 2 weeks until today, but it started last nite,( had to move it to clean it ). I'm pretty sure the dome light drained it , Battery is only couple years old.
    seems strange that this happened all a sudden like , I geuss I will throw another Alt. on it tonight, I have a couple laying around
    Twisted, just called the parts store, there kits only have brushes in them, got to order the Reg.
     
  7. Green hornet

    Green hornet Veteran Member

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    Oct 11, 2015
    North Bay, CA
    Probably just a coincidence. Things happen sometimes.
     
  8. Gary S

    Gary S Administrator Lifetime Gold Member

    20,629
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    Apr 14, 1999
    Bismarck, North Dakota
    The regulator in an internally regulated alternator is a solid state device. They pretty much always fail in an instant. Don't expect a warning from them. Charging the dead battery probably put load on it longer than normal to get the battery charged fully so the regulator could have popped.
     
  9. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

    1,887
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    Sep 11, 2004
    belding,mi USA
    Well now, installed a different Alt.
    Seems things are back to normal
    This happened about 3 hrs ago
    I can barely hold the Alt. , its still that hot , and the hood has been up all along. so is the battery, not as much tho
     
  10. ol' grouch

    ol' grouch Veteran Member

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    Jul 4, 2013
    Evansville, In.


    I'll bet the plates are partially melted inside your battery. When you run way high voltage, it will boil the electrolyte away and expose the plates. I'll bet if you pull the caps and look inside, the level is below the plates and some of them may look melted. This is a sign of a dying battery. If this car is a 1970's vintage system, I'll lay money that the alternator went and cooked the battery and it was probably about half way through it's service life and now is at the end.
     

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