Last week I was sitting in my car for about 30 minutes in the Texas heat with the AC on at idle. I turned off the engine then tried starting it about 10 seconds later but got the clicking sound as if the battery died, and it did. Had to get it jumped and pretty much have been driving with the AC off since then. I just recently took some voltage readings at various stages with the cigarette adapter voltage meter. The car starts and runs fine, but can anyone add their feedback on these readings to determine if it's a battery/alternator/voltage regulator issue? I know a lot of these readings may be irrelevant but I'm trying to provide as much possible information as possible. I haven't checked the readings at the alternator posts yet because it's been raining non-stop. The alternator is most likely stock but the battery is 6 months old. No electrical modifications.
Off -> On (idle) = 12.4 -> 13.8
Idle in Park @ ~750rpm = 13.9
Idle in Park @ ~750rpm w/ fan = 12.8 -> 13.7
Idle in Park @ ~750rpm w/ AC = 12.5 -> 12.4
Idle in Park @ ~750rpm w/ lights = 12.2 -> 12.6
70 mph @ 2000rpm = 14.1
70 mph @ 2000rpm w/ lights = 14.0
70 mph @ 2000rpm w/AC = 14.0
45 mph @ 1500rpm = 14.1
Off -> On (idle) = 12.4 -> 13.8
Idle in Park @ ~750rpm = 13.9
Idle in Park @ ~750rpm w/ fan = 12.8 -> 13.7
Idle in Park @ ~750rpm w/ AC = 12.5 -> 12.4
Idle in Park @ ~750rpm w/ lights = 12.2 -> 12.6
70 mph @ 2000rpm = 14.1
70 mph @ 2000rpm w/ lights = 14.0
70 mph @ 2000rpm w/AC = 14.0
45 mph @ 1500rpm = 14.1