You are welcome. Ya, voltage can be a weird thing. Engine running vintage can be between 13.6 and 14.4 depending how good the charging system is. And how much if a load it is under, i.e. lights, A/C, stereo or all the above. Any electrical/charging system should be able to keep up with all of said loads tho. If it can't, then there's an issue. And that's usually a bad battery, not be able to/keep a charge, or the alt. not charging at all. Then there's the other side, an alt charging too much, 16+ volts, that would be faulty voltage regulator.
2001 Camaro SS LS1
6 Speed Manual
"Concert Hall On Wheels"
"It's better to have it and not need it, than to need it and not have it"