
Originally Posted by
Sabrewings
Faulty voltage regulator in the alternator or faulty alternator. It's simply having trouble maintaining voltage at idle. My car can maintain up to 15+ volts if the battery is low at 650-700RPMs idle. If it isn't giving you problems while driving, then it really isn't a big deal.
Though, I've seen this be a prelude to an alternator that just gives out. Can't say exactly when or even if. But it's possible.