Alternator Not Charging Battery


Old 10-08-20, 01:59 PM
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Alternator Not Charging Battery

1993 Mazda Mx3, 1.6L, Manual, 190K km. Key On Charge light is ON. Engine Running Charge Light OFF. But alternator Not charging battery. All fuses and Fuselinks Ok. Alternator Positive Post to Battery Neg Engine Running 12.63V. Help! Both Battery and Alternator NEW. (Car is Recent purchase)
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Old 10-09-20, 04:40 AM
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Would expect alternator voltage to be 13-15 vdc with engine running. Make sure belt driving alternator is tight. Make sure all connections are tight and cables in good condition in battery/charging circuits. If all is good, take alternator to auto parts store that can test. If test is good, replace voltage regulator (if separate). If test not good, replace alternator.
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Old 10-09-20, 04:52 AM
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Agree with Bob; you certainly have enough miles & years for it to need an alternator. As I recall, the charging light won't illuminate until charging rate drops below something like 11.5V or at least below 12V, so if you're getting 12.63V the light definitely would not come on. Have you tried applying loads to see how it varies? Switch on headlights to high beam, ac blower on high, maybe rear defroster, too, and see what it does. I don't know if external voltage regulators are very common anymore. FWIW I'm getting ready to do surgery on the alternator of my wrecker to replace the internal regulator. My issue is slightly different - good charging, but some mornings when I crank up I'm getting 11.5V until I rev the engine a few times, then it perks up and I'm good. Pretty annoying.
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Old 10-09-20, 05:16 AM
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Who installed the new alternator and battery? Who diagnosed that they were the problem?
Is the voltage regulator part of the alternator or a separate component?
Old 10-09-20, 08:00 AM
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I've been trying to avoid removing/replacing alternator. You have to get at it from underneath and remove most of the undercarriage. But it seems, that's all I have left. Thanks for your reply
Old 10-09-20, 08:11 AM
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Thanks. Supposedly it is a new alternator (it and the battery are the only shiny things under the hood haha). I'll keep plugging away and throw all kinds of load on it, see what it does. When we bought it, I drove it for a 100km or so before it died, tach and speedo went first then it began surging. So I'd say there was a ton of load on it. But seriously thanks for your time. Pulling the alt from this car is a beast. Have to go from underneath and remove half the car before you can get at it.
Old 10-11-20, 03:49 PM
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Make sure you disconnect the battery in the car (AT the battery) before you start the process.
Old 10-11-20, 05:12 PM
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Only the negative battery cable needs to be disconnected Alt repair. If removing the battery both cables are removed of course, but the - first and + last when removing. When installing a battery, the + gets connected first and the - last.
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