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Thread: Wife's G4 just had the battery light come on again after 2 years.

  1. #21
    Senior Member Dirk Diggler's Avatar
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    Fummins, dude, once again! And coming thru with pics like a Japanese design manual. Mother****as like you still give me faith in humanity.



  2. #22
    Senior Member Dirk Diggler's Avatar
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    Quote Originally Posted by Fummins View Post
    I don't believe brake lights would have anything to do with the battery light.

    The battery light will come on for two reasons. It's either overcharging or not charging at all. If it isn't charging, it'll keep running until the battery dies then you're scewed. My first guess would be the common broken wire but you should check other things first...

    First and easiest thing to check is make sure you still have a belt... If you're belt broke, you're gonna have a bad time.

    If you still have a belt, the next thing I'd do is finger out if you're battery is being charged or not when the engine is running. Start it up and throw a volt meter on the battery. It should read between 13.5 and 14.5 volts(when engine is running).

    If it's reading closer to 15Volts then you probably have a broken somewhere in the wiring harness between the alternator and ecu.
    The most common place for them to break is in the wiring harness along the top of the intake manifold. Usually near where the harness is zip tied from the factoria. Wires vibrate and chafe through, then hang on by a thread. One way to check if this is your problem(not a sure fire way) have someone sit in the car(running) and wiggle the wiring harness around. If light flickers or turns on and stays on then that's probably your problem.
    Easy cheap fix. Find broken wire then repair it. Might have to splice in a little chunk oh' wire.

    If it's under/not charging I'd still take a look at the wiring harness. That could be the problem too. I've yet to see a bad Mirage alternator but that's not to say they can't go bad. I'd check the wiring first before throwing a new or even a used one at it.

    This post is probably way longer than it needs to be.
    It was at 12.5 V after a drive around and revving it up past 2500 rpms. She's purring, for now.

  3. #23
    Well I didn’t see that coming.
    Are you saying it’s showing 12.5v while it’s running or not? It should be higher when it’s running.
    Mirage videos:

        __________________________________________

        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)


  4. #24
    Senior Member Dirk Diggler's Avatar
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    Quote Originally Posted by Fummins View Post
    Well I didn’t see that coming.
    Are you saying it’s showing 12.5v while it’s running or not? It should be higher when it’s running.
    Our initial readings before test drive was 12.5 volts. It tested 13 volts after a 15 min fast drive.

  5. #25
    Senior Member AtomicPunk's Avatar
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    Quote Originally Posted by Fummins View Post
    Well I didn’t see that coming.
    Are you saying it’s showing 12.5v while it’s running or not? It should be higher when it’s running.
    why is everything corroding so badly down there in Georgia?
    Last edited by AtomicPunk; 05-20-2022 at 12:57 AM.

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    Fummins (05-20-2022)

  7. #26
    Senior Member Dirk Diggler's Avatar
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    Quote Originally Posted by AtomicPunk View Post
    why is everything corroding so bad down there?
    The rest of the engine bay looked good, no corrosion.

  8. #27
    Quote Originally Posted by Dirk Diggler View Post
    Our initial readings before test drive was 12.5 volts. It tested 13 volts after a 15 min fast drive.
    Check it with it running. You won’t blow up or get electrocuted. That wire does looked pretty screwed though so probably is/was your problem. Having 13v I guess shows that it probably was charging. So I guess you could call it goodish.
    Mirage videos:

        __________________________________________

        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)


  9. #28
    Senior Member Dirk Diggler's Avatar
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    Quote Originally Posted by Fummins View Post
    Check it with it running. You won’t blow up or get electrocuted. That wire does looked pretty screwed though so probably is/was your problem. Having 13v I guess shows that it probably was charging. So I guess you could call it goodish.
    We cleaned off the copper wiring and were able to reconnect it to the alternator by crimping it. It should hold but we'll find out. I'd hate to have to spend $2k fixing this at a dealer. It's a thousand just for the alternator alone. Wish me luck.

  10. #29
    Senior Member Dirk Diggler's Avatar
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    Quote Originally Posted by mohammad View Post
    Any idea what happens if you run the alternator without that wire plugged in? i think we had that alternator delete forum thingy that said that the alternator would self excite the field to like 15 volts. If it does then it could be safe to drive with it disconnected for awhile?
    No idea but I'm pissed I've already had 2 corrosion issues in 2 years. The car has been in the rust free south it's whole life, but still I had a corroded battery cable and now this. The car has only 100k km.

  11. #30
    Senior Member AtomicPunk's Avatar
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    Quote Originally Posted by Dirk Diggler View Post
    No idea but I'm pissed I've already had 2 corrosion issues in 2 years. The car has been in the rust free south it's whole life, but still I had a corroded battery cable and now this. The car has only 100k km.
    That's why I was asking about why everything was corroding. First battery terminals, now alternator connector? Here's a thought: your prior bad battery caused the alternator to overcharge trying to compensate for it. And either excess heat and/or current damaged the connector, and it just now got loose enough to kick on the light. From your picture, if the alternator is still good, that connector looks fixable without costing a whole lot. Need a good, experienced independent wrench like Fummins, not the stealership. And still check that wiring harness.


    Last edited by AtomicPunk; 05-20-2022 at 10:20 AM.

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