I have a 2003 GMC Safari (4.3L) and a 2003 Chevy Cavalier (2.2L Eco) with almost identical electrical issues relating to the battery/charging system... I think.
The problem is, neither vehicle can keep a charge on their batteries. One of the batteries is less than a year old so I find it difficult to believe BOTH batteries are causing the issue. I started both vehicles and disconnected the battery to see if the charging system works. Both vehicles run without batteries. I stuck a voltmeter on the ends of the cables and it read a constant 19 volts from the alternator.
Suggestions?