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Thread: Battery light / overcharging

  1. #1
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    Battery light / overcharging

    2014 w/ 155k miles. Original battery, unknown mileage alternator (80-100k ish) replaced original with a used one a couple years ago. Torrential downpour last two days while it was parked (maybe unrelated) Battery light was on when I started it this morning. Drove through some very heavy rain for 10 miles or so. Battery light stayed on, engine missed a couple times. It has missed in heavy rain in the past but not since I replaced the crank sensor. Maybe too much info but including all variables.

    Headed for home when I felt the misfire.

    Alternator output at idle with no accessories running 15.1-15.9v. Unchanged with all accessories on. Disconnected battery terminals. Battery voltage 14.3v. Cleaned and reinstalled terminals. No changes.

    Wiggled all wiring I could see while running. No change.

    Drove to local advance auto for a load test. No misfires, battery light still on. Machine says to replace alternator and battery because battery reserve is virtually zero and alternator is overcharging.

    New/used Alternator will be here tomorrow.

    Am I missing anything? Guess I should be ready to dissect some wiring if it isnÂ’t fixed with an alternator and battery.



  2. #2
    I had one car overcharge like that. The wiring harness that runs along the front of the engine had a broken wire where it was zip tied from factory. Might be worth a look. The one I found was in the harness near where it curves and runs along the top of the transmission(the zip tie closest to the drivers side of the engine). If that makes any sense? It was overcharging and making the battery light come on, after wire was repaired it went out and charged normally (14.3v ish)

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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  4. #3
    Quote Originally Posted by dustyb View Post
    2014 w/ 155k miles. Original battery, unknown mileage alternator (80-100k ish) replaced original with a used one a couple years ago. Torrential downpour last two days while it was parked (maybe unrelated) Battery light was on when I started it this morning. Drove through some very heavy rain for 10 miles or so. Battery light stayed on, engine missed a couple times. It has missed in heavy rain in the past but not since I replaced the crank sensor. Maybe too much info but including all variables.

    Headed for home when I felt the misfire.

    Alternator output at idle with no accessories running 15.1-15.9v. Unchanged with all accessories on. Disconnected battery terminals. Battery voltage 14.3v. Cleaned and reinstalled terminals. No changes.

    Wiggled all wiring I could see while running. No change.

    Drove to local advance auto for a load test. No misfires, battery light still on. Machine says to replace alternator and battery because battery reserve is virtually zero and alternator is overcharging.

    New/used Alternator will be here tomorrow.

    Am I missing anything? Guess I should be ready to dissect some wiring if it isnÂ’t fixed with an alternator and battery.
    Here, take a look before throwing an alternator at it.

    https://mirageforum.com/forum/showth...ttery-Light-On

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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  6. #4
    Moderator Eggman's Avatar
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    Also check your ground wires and straps though the broken wire is more likely to be the cause.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    You nailed it!
    Cut the first factory wire tie on the passenger side of the motor harness, it didn’t look good...

    Opened it up and one wire going to the alternator was broken and a few others were worn almost through. The rest of the harness back to the transmission looked good. A little solder, shrink tubing and electrical tape later, it was running like a champ. No battery light and alternator output was down to 14.6v.

    Fummins I can’t thank you enough. Not only for the money you saved me by not buying an alternator, but for all the frustration and possibly a new car payment I avoided by following your advice. If you’re ever in the pittsburgh area contact me to claim the brewskies I owe you.
    Thanks again,
    DustyName:  584F3D22-57E3-49B1-A40C-5D0DFD33ED66.jpeg
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    Senior Member Top_Fuel's Avatar
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    Can you post a better pic of exactly where that harness is? I thought the original thread had pics but I didn't see any there.

    Did you at least replace your 7 year old battery?

        __________________________________________

        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)


  13. #8
    Senior Member Dirk Diggler's Avatar
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    Quote Originally Posted by dustyb View Post
    You nailed it!
    Cut the first factory wire tie on the passenger side of the motor harness, it didn’t look good...

    Opened it up and one wire going to the alternator was broken and a few others were worn almost through. The rest of the harness back to the transmission looked good. A little solder, shrink tubing and electrical tape later, it was running like a champ. No battery light and alternator output was down to 14.6v.

    Fummins I can’t thank you enough. Not only for the money you saved me by not buying an alternator, but for all the frustration and possibly a new car payment I avoided by following your advice. If you’re ever in the pittsburgh area contact me to claim the brewskies I owe you.
    Thanks again,
    DustyName:  584F3D22-57E3-49B1-A40C-5D0DFD33ED66.jpeg
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    Yeah Fummins is pretty much a saint in the amount of money he's save folks on here. Are those chew marks on those cords?

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    She made it to work again today. Running great.
    Before and after pics below. In the after (top) pic the light is focused on where the break was. It was the first zip tie on the harness on the passenger side of the valve cover. The offending factory zip tie snaps into that rusty tab on the intake. They look chewed but they were all rubbed through by the edge of the zip tie. I believe Fummins break was the last zip tie on the driver’s side (where the magnet is pointing in 2nd pic). And yes, I did splurge on a new battery. Mine was definitely on borrowed time. Name:  7B9E0366-CF36-4B8B-A231-7C86A746C929.jpeg
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    Last edited by dustyb; 03-03-2021 at 03:40 PM.

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