From 440_Magnum, 2) Often overlooked- a short-to-ground in the "return" wire (usually green) to the PCM from the alternator can cause the alternator to go into full-charge mode.

This sounds like my case... only in that thread they say the gauge in the dash says over charge. mine is opposite. I get over charge at battery, under charge in dash. PCM thinks battery isn't charge enough so it keeps pumping more into it... what the hell do I do?