Is my alternator bad?

So I drive my parent's old car. It is a 2000 Chrysler LHS, 150000 miles, and to my knowledge we have never replaced the alternator. I got up to go to school this morning and the battery was dead. We jump started it and then I drove to school but then it was dead after school again. A buddy of mine gave me a jump and then I drove home. When I was coasting I put it in neutral and kept the rpm up slightly to charge the battery. The ride from my school is about 10 minutes. I immediately pulled into my driveway shut my car off and tried to start it again, but yet again, the battery didn't have enough power to start the car...

Is my alternator bad?

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  • 7 years ago
    Favorite Answer

    Take both your battery and alternator to the nearest auto zone or parts store. They will check it for you and let you know what you need. But start there because they are very easy to replace.

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  • David
    Lv 6
    7 years ago

    A 10 minute drive isn't really enough to recharge the battery, even if the alternator is good. If all you ever do is the school run, the battery will get flatter and flatter as starting it uses more stored power than the alternator can replace.

    Back to your story - if it started with a jump start and continued to run then something was producing enough power to keep the car going. My guess is that that something was the alternator.

    So charge the battery.

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  • 7 years ago

    You need to get the battery on a battery charger, unless you like the potential of damaging your alternator by overworking it, and if not get it fully charged, minimum 2 hours at 10 amps, best is 12 hours at 2 amps.

    While the battery is charging clean the battery posts and terminal ends with this tool...

    http://www.walmart.com/ip/16006673?adid=2222222222...

    Tighten the terminals back on as tight as you can, and now you can see if you have another problem like the alternator. The car will die in a couple days if the alternator is bad.

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  • Irv S
    Lv 7
    7 years ago

    Could be the alternator, could be the battery.

    If 'keeping the rpms up' showed an indication of battery charging

    then more likely the battery is at fault.

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  • Anonymous
    7 years ago

    Either --the battery is NOT--chargeable..

    Or..the alternator--is not sending DC-voltage output from the rectifier/

    ===

    You need to remove the 12-volt car battery..

    Place it on a wooden board..

    Attach a 12-volt battery charger--using 2-amps..or 6-amps..

    Let that run its charge--for 4-6 hours../

    ...if your battery charger uses a NEEDLE--the needle will drop to [ zero ]

    Confirming--a FULL charge../

    If the needle--never moves--the battery--is completely defective../

    ===

    Testing your alternator--is best with a brand NEW battery../

    Install the battery--

    Using a Multi-Tester../

    Test the battery--for a Standing Charge..

    Best battery=13.2 volts

    Risky battery=12.4 volts or lower../

    An OK battery=12.7 volts..

    ===

    Leave the Multi-Tester attached..

    ..have somebody start the motor..

    The Multi-Tester--should jump--to--14.4 volts..

    ---that is your charging circuit.

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  • JJ
    Lv 6
    7 years ago

    It is the battery

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