I have 06 2500. If I am stopped and the truck idles. The lights slowly dim and the batt gauge starts to drop from 14 down..it gets to about 8 and the truck idles back up and the lights get bright again. Has anyone had a problem with this?

 

It sounds normal. I think your preheater grids are being triggered while you are stopped. They draw a lot of current and will dim the lights as they cycle. The post-heat cycle stops when you are above 18 MPH.

 

^^what he said
your truck is fine.

Mark