Maybe someone can shed some light on this. My voltage readings never stay the same. Now when I say that I understand there will be some fluctuations. Mine as normal when starting begins st 12.8 then slowly gies up to 14 but through out my trip to Belgium the readings would go anywhere from 12.5 back to 14 then slowly drip to 13 an back to 14 an so on. My 300C keeps a steady 14.1 with very little fluctuations. On the last leg of my 12 hr drive to Belgium my voltage went down to 12.8 and stayed there till I arrived. 2 days later dead battery. Driving the car daily starts ok with the voltage readings fluctuating between 12.5 to 14 all day. I do not dare leave tge radio o while parked for fear the car will not start. As mentioned in another thread the alternator an battery have tested ok and undsr a load showing the alternator is charging. I am going ti hook my aeoforce gauge back up so I can observe my amps. I read this is another way to test if the regulator on the alternator is working correctly. Do not know if the gm has a regulator on there alternators or if its just the earky model cars that had this. Anyone shed some light on this. Something comes to mind on me is maybe my alternator belt tensioner is going out. Guess I will see that when replacing belts. Anything I should look for in particular when looking at the tensioner, apart from the obvious?