1994 Ford F-150 battery keeps overcharging then dying

Hi billymac here. Well sounds like most likely you have a bad alternator or possibly a bad regulator. However with this paticular vehicle there is other things that have to be checked. If the batt is good and fully charged and runs completely down overnite you have a pretty good draw. And a draw like that will cause heat. So something will be hot in the morning. Before you start your truck raise the hood touch the alternator regulator and the a/c compressor. Put your hand on the steering coloumn the cruise control and the heater motor if any of these items are hot that will be where your draw is comeing from. If a mechanic was trying to repair this prob he would do a draw test to see exactly how many amps of draw their is. This requires some special tools. But if you turn truck off close all the doors make sure no lights are on. Disconnect the neg batt cable touch the cable briefly as in rub the cable end against the neg batt post you will see a spark a spark like from a lighter is normal. However one like jumper cables make is too much. Your chargeing system should never go beyond 14 volts. Since yours does this points directly to the charge system. I hope this helps. Billy mac