HOW DO I CHECK IF THE ALTERNATOR IS WORKING?

Tiny
WALT
  • MEMBER
  • 2005 BMW X5
  • 63,000 MILES
BATTERY LOW; LOST CHARGE; IS IT BATTERY OR CHARGFING SYSTEM?
Tuesday, January 10th, 2012 AT 2:33 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
Measure the battery voltage with the engine off and with it running. Off must be 12.6 volts. If you find 12.0 volts, it's okay but discharged. Closer to 11 volts means a cell is shorted and the battery must be replaced.

Engine running, the voltage must be between 13.75 and 14.75 volts. If it's low, suspect the generator.
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Tuesday, January 10th, 2012 AT 2:39 AM

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