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3G Alternator Question

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Kizer, May 18, 2020.

  1. Kizer

    Kizer Supporting Member Supporting Member

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    Hello All,

    My 2nd replacement alternator (in two months) is "pushing" 12.4V after start up.
    After I reach 3000 (or so) RPM it charges at 14.2V until I shut the engine down.
    Upon start up it's back to 12.4V ... etc.

    What causes this problem?

    I'd like to understand the issue before I go back to NAPA.

    Thank you in advance,
    Kizer
     
  2. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    My only thought is that the alt isn't seeing the load properly. Which would mean the sense wire isn't in the right spot or otherwise the 3G is wired up wrong... I'm no electrical guru though. Maybe a loose connection even. Here's a good diagram of the conversion if you aren't sure already:

    [​IMG]


    A good 3G setup will charge correctly(14.2ish) from idle to WOT right out of the gate. I'd know, I have one! :)
     
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  3. Kizer

    Kizer Supporting Member Supporting Member

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    Thank you!
     
  4. Kizer

    Kizer Supporting Member Supporting Member

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    Update: The second failed alt. was returned to NAPA. The one that they offered for replacement tested bad too!!
    That's three straight! What are the odds ..??
    Anyway #4 was (is SO FAR) a winner.

    What (who) are y'all using for replacement alternators?
     
  5. chillman88

    chillman88 Supporting Member Supporting Member

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    Apparently not

    Need
    Another
    Part
    Again

    I've used Advance Auto when I need something quick. Always be really nice to them and they can test it before you leave ;)
     
  6. Kizer

    Kizer Supporting Member Supporting Member

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    That's how I found that #3 was bad.
    I didn't even have to ask.

    Apparently not what?

    Thank you.
     
  7. chillman88

    chillman88 Supporting Member Supporting Member

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    Napa. also known as:

     
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  8. Kizer

    Kizer Supporting Member Supporting Member

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    Got it ... now.
    Guess I'm a little slow after my celebration beers!
     
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  9. chillman88

    chillman88 Supporting Member Supporting Member

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    That's alright. One of the guys at work made an inside joke today and it took me entirely too long to figure it out so we're in the same boat LOL
     
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  10. Kizer

    Kizer Supporting Member Supporting Member

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    Thanks.
    At least yours isn't (wasn't) in writing!
     
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  11. chillman88

    chillman88 Supporting Member Supporting Member

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    I prefer no evidence, but I'm not "usually" that lucky LOL
     
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  12. aggiediesel01

    aggiediesel01 Full Access Member

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    The_Josh_Bear, chillman88 and Kizer like this.
  13. Kizer

    Kizer Supporting Member Supporting Member

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  14. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Unfortunately NAPA has gone way downhill in the last...10 year? I dunno I'm no mechanic but they used to be the spot to go to, now they are full of bad-out-of-the-box crap like everyone else. And in a stunning turn-around, O'rielly Auto has upped their game A BUNCH in the same time frame without upping the prices significantly. Can't say much about the other parts houses.

    +1 on DIY rebuild! But also for starters, I've read over and over from guys that know the deal that if you can find a good repair shop for alternators/starters they last forever and actually WORK. I have nothing close to me like that I am aware of.
    I bought a 3g alt from a salvage yard 10 years ago and I've rebuilt it twice because the first time I "rebuilt" it I didn't have the bearings so I only did half the job. Then the rear bearing failed me a few months ago. It was missing when I lost charge and didn't break anything somehow! Easy rebuild after that, this time with bearings!
     
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  15. chris142

    chris142 Full Access Member

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    Napa's rebuilt starters and alternators are pure garbage. A guaranteed comeback. They ship the cores to china to be rebuilt. Most others ship to mexico and occasionally usa( both with global components).

    At least autozone gives you a roadside guarantee of their part fails.

    IMO the only thing to buy from Napa is the gold oil filters,batteries and belts.

    Everything else is the same crap the other places have but with inflated prices.
     
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