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Thread: Electrical issue, not battery, not alternator

  1. #11
    Senior Member daleWV's Avatar
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    it sounds to me like the carbon brushes that ride on the slip rings inside the alternator may be just about worn out. When that happens one minute the alternator is working fine then the next not at all then the next it's working fine. This can happen for quite a while until the brushes are completely gone.



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    Quote Originally Posted by daleWV View Post
    it sounds to me like the carbon brushes that ride on the slip rings inside the alternator may be just about worn out. When that happens one minute the alternator is working fine then the next not at all then the next it's working fine. This can happen for quite a while until the brushes are completely gone.
    Agree!
    However it doesn't explain random lights in the dash comming on...

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    Ok,
    So I started tracing wires, started with the plug into the alternator. The white wire was bound too tight in the zip tie, and corroded or was otherwise incentivised to break inside the insulation.

    I pulled on the insulation and it stretched where the hole was, obvious break in the wire.

    Removed 1/2 inch of insulation on either side, soldered in a jumper wire, now charging at almost 15 volts, instead of previous normal of around 14.

    It took around 120k miles for this to happen, but I expect to see a lot more of this, now knowing what happened.

    Pictures are of the basic process, the zip tie is what was holding the bundle, the last one was the 'over tape' and the hole rubbed in that.
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    AtomicPunk (02-10-2020),Brianm13 (07-18-2021),Cobrajet (02-10-2020),Fummins (02-09-2020),Macmoto (02-10-2020),Top_Fuel (02-09-2020)

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    Thanks for the insights, everyone! You helped me save my sanity. Seriously, I was getting ready to trade it in, or go to a shop. I can't afford either of those. I love you all!

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    Senior Member Top_Fuel's Avatar
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    This the area where the wire wore through...where the wire is bundled and attached to that metal flange thing?

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    Quote Originally Posted by Top_Fuel View Post
    This the area where the wire wore through...where the wire is bundled and attached to that metal flange thing?

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    Just spent a few hours plowing & blowing snow. To tired to go back outside. Does anyone suggest a preventive measure to take for that area?

    Loosen the bundle, wrap the wires with something? Thoughts?

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    Yes, that's the right spot. I would think that loosening the zip tie a couple clicks would do it, to take pressure off the insulation. You'll still get rubbing, but hopefully not enough to break down the insulation.

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    Quote Originally Posted by Mark View Post
    Just spent a few hours plowing & blowing snow. To tired to go back outside. Does anyone suggest a preventive measure to take for that area?

    Loosen the bundle, wrap the wires with something? Thoughts?
    Also, your engine bay is beautiful!

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    Congratulations on finding it, and thanks for the warning to check cable ties!
    There have been a few cases of wires breaking where they were tied.

    Temperature very much affects the properties of lead-acid batteries, and Japanese car makers were the very first to have the charging voltage adapt to temperature. In the cold, 15V is normal for charging. In the summer you could expect 13.8V or so to be enough. More than 14.4V at 20°C and the battery will discharge gases and lose water. The voltage when gassing begins is just as temperature-dependant as the voiltage needed to get it charged.
    Last edited by foama; 02-10-2020 at 08:43 AM.

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    Senior Member Top_Fuel's Avatar
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    Just another reason to have a Scangauge and have one of the 4 readouts set to display a voltmeter.

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        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)


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