Volt meter has always been 14 solid now it's up to 15.1 at batts with multimeter. Origional alt and batts I guess it's time for new alt not much sense in trying to repair it.

 

Could be ECM. The ECM controls the voltage output from the alt.

 

Prob not a alt problem. Maybe your crossover cable is corroded and is not charging both batteries equally. More than likely, not charging the driver side battery. The ECM sees low charge on driver side battery and increases the charging level. I would clean, then check the crossover cable for continuity with a voltmeter.

 

It will charge more in the cold weather. Nothing to worry about. It's a Dodge thing. May be time for batteries real soon. Alternator is fine.