Don't really know ,sending out to a rebuild shop , never seen this type of problem before...thinking voltage regulator diodes breaking down in extreme cold conditions ....New alternator on now for over 24 hours Notice battery holding at 12.6 volts , will be out of town a few days will recheck upon returning.... it had been dropping below 12 volts with old alternator...even through diodes test showed good when checked , could still be leaking at colder temperatures...will see what the starter/alternator repair shop finds if anything.,. It turns free with no noise really don't think it's a bearing issue but could be wrong....