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Old 10-07-2013, 02:20 PM
bmwoem1 bmwoem1 is offline
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Location: New York
Join Date: Jan 2013
Posts: 725
Mein Auto: X3
Transfailsafe, ABS indicator, 4x4 indicator dash lights - recently changed batt

It's the alternator overcharging when it gets hot. It will test good until you check it when the problem is actually occurring. The whining sound can also be caused by excessive AC voltage in the audio electronics. The batteries you are replacing are getting cooked by the overcharging alternator. At the very least, replace the alternator voltage regulator if you don't want to spend the money on a whole new one

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