Electrical issue

Discussion in '2005+ Ford Mustang v6 4.0L Tech' started by Martin Huerta, Jan 26, 2022.

  1. Martin Huerta

    Martin Huerta Junior Member

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    Recently changed the alternator and everything was perfectly fine until recently whenever I am full throttle all electrical systems turn off like radio, AC, headlights, dash lights everything. It will do it only full throttle. Anyone know the issue?
     
  2. 86GT351

    86GT351 forum member

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    What brand Alternator did you use? I have seen faulty Alternators recently.
     
  3. DieHarder

    DieHarder Senior Member

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    Yeah, definitely weird. Are you sure something isn't loose or being stretched somewhere? I would go thru the alt/battery/ground cabling; loosen and re-tighten all connection points for the alternator/battery/grounds and any other bolts/nuts you touched when you changed it out. Check voltage output of the alternator across the battery looking for voltage drops from the alternator body to the engine block and then from the alternator body to the passenger strut tower ground. If that all checks out may be the alternator but unusual it would fail only at full throttle.
     
  4. Martin Huerta

    Martin Huerta Junior Member

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    It was a duralast alternator
     
  5. Bullitt 4641

    Bullitt 4641 Junior Member

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    Just a guess, but I'm thinking it could be an over-voltage condition with a bad voltage regulator allowing the charge voltage to go too high during full speed rotation of the alternator.
     
  6. Juice

    Juice forum member

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    While I agree with this, I had the exact opposite issue on my fox. Charged fine street driving. But on track, I watched the volt guage drop to 6 or 7 volts near/at redline.
    Either way, it sure sounds like a voltage regulation issue.
     
  7. Rugermack

    Rugermack Junior Member

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    Would slowing it down with under drive pulleys help ?
     
  8. Juice

    Juice forum member

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    That would be a 'bandaid' fix. Something is not right. And computers dont like out of spec volts.
     
    Rugermack likes this.
  9. DieHarder

    DieHarder Senior Member

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    Quickest way to know for sure what the issue is..., is to swap it out. Unlikely symptoms will be exactly the same unless there's something fubar with wiring or another subsystem.
     
  10. Juice

    Juice forum member

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    Voltage is controlled by the pcm.
    But I do believe the module on the back of the alternator has the actual controlling chip. So, I would say get a replacement regulator and swap it out.
     
  11. SVT Rider

    SVT Rider Member

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    AutoZone's alternators (duralast) are a crap shoot. The only good thing about them is the warranty, but you will be constantly changing them out from this point on, especially if running at high RPMs.

    Many, many reports of an alternator going bad right after installing, as these are remanufactured alternators these days. Swap out for another alternator as someone suggested; easy to do with the AutoZone warranty.
     
  12. Juice

    Juice forum member

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    What I want to know is how many of these new alternators that were installed and went bad shortly after is:
    Did the battery get fully charged up, or did they just charge a dead battery with a new alternator?

    I would EXPECT an alternator to fail if you tried to charge a dead battery up. Sure, it may seem like the battery is charged because the car started. I could be deeply discharged and still crank/start.
     
  13. SVT Rider

    SVT Rider Member

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    I totally agree. Even worse if a cell was shorted in the battery, which I have seen it more than once when a alternator fails. I tend to replace the battery when an alternator fails, especially when the battery is a few years old. Critical components like these are just too expensive to have one take out the other or be weakened after a repair.
     
  14. Juice

    Juice forum member

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    I get a little OCD about batteries. Got a bunch to maintain (cars, bikes, toys). 2 solar chargers and a Batt Tender get rotated regularly this time of year. lol

    If kept charged, batteries last. Running them down kills them.

    And these new cars drain a good battery in about 2 months. Something to keep in mind.
     
    Last edited: Feb 2, 2022
    Midlife Crises and SVT Rider like this.
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