Battery not holding charge

Tiny
WYLIE
  • MEMBER
  • 2000 SAAB 9-5
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 31,000 MILES
The battery went dead. When I start the car with a jump, and the car is running, and I disconnect the positive pull on the battery, the car dies. I think it is the alternator, what do you think?
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Tuesday, March 22nd, 2011 AT 11:27 PM

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Tiny
CARADIODOC
  • MECHANIC
  • 33,699 POSTS
I HOPE it's the generator because if it was working, disconnecting the battery cable can destroy the many computers on the car from excessive voltage. That was a trick done many years ago by mechanics who didn't understand these systems. A better and safer test is to use an inexpensive digital voltmeter to measure battery voltage. With the engine not running, a fully charged battery will read near 12.6 volts. If it is closer to 11.0 volts, suspect it has a shorted cell. With the engine running, the voltage must be between 13.75 and 14.75 volts. If it stays near 12.0 to 12.6 volts, suspect the generator or voltage regulator.
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Tuesday, March 22nd, 2011 AT 11:42 PM

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