Diagnosis Help Needed: Battery or Alternator?

Earl_H

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Had the Viper out yesterday after about 2 weeks of inacticity. Drove it to the gym (~ 20 miles) no problem. On the way home the battery voltmeter went to 0, the rpm guage went dead, the radar detector started to pulse off/on, radio eventually went out. Then the battery light came on. Got the car home, turned off the ignition. Tried to restart but the battery went dead. Put a recharger on the battery for about 3 hours and then sucessfully restarted the car. Does this sound like an alternator problem or a battery problem?
 
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Earl_H

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Let the engine idle for about 15 mins. and the volt meter went to 0, car still ran.
 

luc

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make sure that your battery connections are tight and connect a voltmeter whith the engine idling.
Volts shoud be above 13.5/14.
If not, problem is with your charging system.

Luc.00GTS
 
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Earl_H

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Strange thing...AEM reads about 9.5-10volts. When I use a voltometer it pegs at 15v.
 

Randy

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One way to test - disconnect the battery at the engine compartment battery connection and put a charger on it (the battery cable, not on the connection to the car :cool: ). Let it sit on the charger for a while (a number of hours at least), then disconnect the charger (leaving it disconnected from the car), and let it sit some more - overnight perhaps. Then re-attach it to the car and see if it will start the car. If it starts the car, meaning the battery is accepting *and* holding the charge, it would seem to be the charging system. If it won't start the car, its likely the battery. Or, you can take it to a place that has a battery load tester and save a bit of waiting time.
 
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Earl_H

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Turns out it was the AEM, replaced Alt. and Speedo for nothing...well it was a good exercise in learning more about the Viper electrical system. Live and learn. :)

Thanks to all that offerred help on this (especially JD).
 

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