How do I test an alternator without a voltmeter?

My 2015 Kia Sorento has had trouble starting recently, as if the battery is low. Thing is, I just replaced the battery last year, so I think it could be the alternator. How can I test the alternator if I don’t have a voltmeter?

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Answer provided by
Laura Salvas
Answered on Apr 28, 2022
Sorry your Kia Sorento is causing you trouble! Fortunately, there’s no need for you to run out and buy a voltmeter, as there are a few ways you can test the alternator using just your gas pedal, car battery, car radio, or your ears.
Here’s how to test an alternator without a voltmeter:
  • Rev the engine to 2,000 RPM. If the voltage or ammeter gauge on your dashboard has a high reading, the alternator is charging the battery.
  • With your engine running and using extreme caution, disconnect the negative battery cable (you can loosen it in advance). If your engine keeps running, your alternator is okay.
  • Turn your car radio to the lowest AM frequency, turn the volume down, and put your foot on the gas. A buzzing sound coming from your speakers could indicate an issue with the alternator.
  • Keep your car idling and lift the hood. If you hear a squealing sound coming from the alternator, there might be an issue with the belt.
If you suspect your alternator isn’t working properly, it’s just a short time until your battery dies and your car will not be able to run.
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