I have an 05 1500 crew cab 5.3. About every other day after driving about 15 miles the volt gage drops from like 14.8 to 13.2 or so. It stays like that til I turn it off if I restart it, it’s goes back to 14.8. The battery is good. New alternator. I’ve checked out all the grounds I could find. I don’t know if it’s a coincidence or not but seems to do this when I adjust the climate control before driving. Anybody have this type of problem? Oh I’ve also put in a new ecu.

 

Sounds completely normal. The charging system automatically adjusts output to the conditions. Nominal battery voltage is 12.7V so no problem here.