[GTP Dad]

There are a couple of items that can cause this. Start by checking the wiring to the alternator and to the starter, battery and power control center under the hood. If everything is clean and tight then you may want to check the belt as it could be slipping causing the alternator light to give you intermittant charging. Finally it is possible that the voltage regulator inside the alternator is going bad. I would check all the other items first since that is a long shot.