what causes an alternator to overcharge
A malfunctioning external regulator does not disengage properly, which causes the alternator to overcharge, AA1Car.com explains. This is the part of the alternator that regulates the amount of electricity the vehicle needs to perform at varying speeds. Alternator output is another reason for overcharging. Re-manufactured and replacement alternators are larger in size and offer a higher output than stock alternators. This causes inefficiency in the pulley on the belt drive, which causes the alternator to rotate more.