99 corolla seca.
OK so first time it happened i was driving and i suddenly lost power (electrics / everything else) it just kind of putters a little and then that's it.
I called roadside assist and we jumped her and tested everything. and the numbers looked good. figured it was a buildup under the battery terminal possibly causing the problem, we gave that a good clean.
a couple of days later i was paranoid so i got the multimeter out just to check again while it was in the driveway, 12.8v without the engine turning over and 14.1V with the engine on. seemed nominal.
well today it just happened again, roadside assist looked at it and everything seemed fine again. perhaps it's something to do with the heat? (summer here atm) both times i had the AC running with the fans on. I'm a little stumped, perhaps the alternator is failing but only after warming up...
so i thought it was probably the battery so i replaced the battery, and with a new battery in the car while i was driving initially i read 13.9 volts at the lighter with a multimeter
but shortly after for a while it droped to 12.3 which prompted me to go home, in the driveway though it went back to 13.9
does anyone know if perhaps the charging system is realising the battery is full and just disengaging the alternator for that time? or does this indicate i have a definite issue with the alternator?