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Auto Parts and Repairs
Car Batteries
Toyota Camry

How do you know an alternator is bad?


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Wiki User
June 22, 2011 10:50PM

unplug the negative battery terminal while the vehicle is still running.......if it dies, then more than likely the alternator is bad. if it still runs then the alternator is prolly still good

That procedure can damage today's alternators. Better off using a voltmeter and test battery voltage at the battery before you start vehicle then again after it is running. A fully charged battery should read 12.68 Volts and if the charging system is healthy, 14.5 Volts while it is running. If the battery is not fully charged you will not get an accurate reading of the charging system.