Noticed here recently that my volts don't sit at 14V, but rather float between 13-13.4V. Got a voltage reading of 12.9V with my code reader with headlights on, radio on, blower motor on, and wipers on. It seems low to me, but I've tested it at work (Advanced Auto Parts) with our machine and she passes every time.

Do these XJs just naturally float around this range, or is this the sign of an alternator starting to give way?

I plan on doing the Big 7 upgrade to the battery/starter/alternator wiring in the near future, if y'all have a similar problem that that upgrade cleared up, let me know!
Appreciate all the help y'all have been giving me.

 

All those numbers sound good to me. Among other things the voltage varies with temperature... remember the temperature sensor under the battery....