04 4.0 lights pulsing, overcharging

[Erikthered]

Yesterday started the truck and the lights were pulsing and the battery light would flicker, got it home and found out it was charging at over 15/15.5v. Checked forums and troubleshooting and figured voltage regulator. Replaced alternator and same thing happened for a bit (pulsing and 15+v) but then charging dropped to 12.3v. (12.8v while not running) About ready to go back to Jeeps. Any ideas?

 

[Erikthered]

Update, brought the battery and old alternator in for testing. Both tested good! WTH. Put the battery back in, started it, 14.7v, no pulsing. All I can think of is old alternator has a bad rectifier, battery was out long enough for computers to reset. Whatever.