How do I know if my alternator is bad

Tiny
GORDIN
  • MEMBER
  • 1995 MAZDA MPV
  • 12,000 MILES
Changed the battery for a new one also changed the starter and gave it a tune up
Sunday, February 26th, 2012 AT 7:36 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
Why do you suspect it's bad? What's the symptom?

To test the system you need a load tester but you can start by measuring battery voltage with an inexpensive digital voltmeter while the engine is running. It must be between 13.75 and 14.75 volts.
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Sunday, February 26th, 2012 AT 9:15 PM

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Got a red battery warning light on? This most likely means the alternator has gone out and needs a replacement. To confirm the failure use a voltmeter to test the alternator...
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