I’ve got a 2004 5.9 6 speed Cummins with a deck on it! I’ve got a problem with the signals from what I think is a voltage problem from the alternator maybe?... when my truck is NOT running and I just turn the key to on position all my lights and signals work perfect but when I start the truck my interior lights will be on normally(that’s if truck door is open) and all of a sudden a few seconds later they will get instantly a bit brighter and the blower fan actually speeds up as well and at that same time when a try my signals that’s when they start to blink really fast depending which signal I try and my rear signals do like a quick pulse!!... when it’s idling this will happen on and off, the signals will work normally one second then they start blinking really fast for a while again then back to normal and so on, but when I actually drive the truck around the signals are always blinking fast and it’s not good! Any help would be awesome, thanks!!