High voltage

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by H-Town Trucking, Jun 15, 2021.

  1. H-Town Trucking

    H-Town Trucking Bobtail Member

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    Sep 25, 2020
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    What would be causing high voltage?? Bad alternator?? Any help would be appreciated thanks 2007 KW W900
     
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  3. Goodysnap

    Goodysnap Road Train Member

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    Yup. Internally regulated. Alternator will not shut off. I would double check with a meter at the hot post to confirm high.
     
  4. joey8686

    joey8686 Light Load Member

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    Alternator, we just had this happen a few months ago
     
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  5. roundhouse

    roundhouse Road Train Member

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    if there not bad or shorted yet. They will be soon if you keep driving it
     
  6. AModelCat

    AModelCat Road Train Member

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    Canuckistan
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    I wouldn't toss an alternator at it without running a few voltage checks first. I've seen trucks where the voltmeter on the dash pegs out at 15+ volts but only putting 13.5 to the batteries because of a rotted battery cable end. Alternator was 100% fine. Diagnose before throwing money at a problem. Just because 7 other people had the alternator as the issue doesn't automatically mean yours will be too.
     
  7. Rideandrepair

    Rideandrepair Road Train Member

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    Mine was running high because of one shorted battery. Wasn’t as high as yours, and wasn’t consistent. Thought it was the guage. I kind of ignored it, till an obvious sulphur smell on a real hot day got my attention. I would guess disconnecting the batteries would tell right away if you have a battery or cable problem. I disconnected the bad one till I could get 3 new ones.
     
    Last edited: Jun 19, 2021
    Dave_in_AZ and Artax Thank this.
  8. MLC Adventures

    MLC Adventures Medium Load Member

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    Make certain all batteries are getting the same voltage first. If they are, bad alternator.
     
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