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Q: What voltage should the alternator put out at idle?
What voltage when reved up? on 2001 Lexus ES300

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I'm getting 13.6 volts at idle but when I rev the engine the volts drop below 13 volts. The battery may be bad as it only reads 10 volts with engine off.
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Have the battery tested both with a hydrometer and high rate discharge test to see if it is good (probably not. At rest voltage for a fully charged "good" battery is 12.6 volts an alternator that is charging will read 14.6 approx across the battery with the engine running. also take a reading at the large B+ alternator terminal and see if the voltage is higher there indicating bad connections.
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