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Q: after replacing the alternator with a new one all warning lights still on why ? on 2006 Hyundai Sonata

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I've checked all connections and fuses , thought maybe the computer would have to be reset but I can still disconnect the battery cable and car goes dead , that tells me its still something with the alternator but what ?
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DON'T disconnect the battery while it's running. that may cause a voltage surge that can damage computers etc. Did you install a factory alternator or aftermarket? did you FULLY charge the battery before starting it with the 'new' alternator.Use a voltmeter while running to test voltage. Use service manual for reference points. If you have access to a scanner with live data , that may be more helpful. many vehicles alternators are controlled by the PCM , the original alternator may not have been the problem.
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