So the first time I went out for a drive, noticed my voltage needle fluttering around 13, not the solid 14 I always see. Was around 100 that day, car reading 110. 3-4 other days I've been out in same temps, same thing.

The one cool day, 75-80 evening, my voltage was sitting nice at 14.

Needle fluttering seems to have stopped thankfully, but it seems to stay at 13 on these hot days.

Input? Alternator not working as well in heat, battery? AC taxing the system?

Thanks in advance...