I have a 2006 Dodge 2500 (Megacab). The lights (both headlights and interior lights - dash lights, etc.) dim and then become brighter, dim again. Both batteries are new. Could this be an alternator problem? I have had problems before with my TIPM box, could this be associated with that?
Does this happen at all times, or just when the truck is started and not warmed up yet? If it only last for a minute or two at startup, it's your intake grid heater doing it's job.....completely normal.