When traveling at highways speeds (during the winter) the passenger is getting a cold draft on his/her right side. Any ideas on how to solve, or where its coming from? I can't find anything obvious. 2006 Ram 3500 Quad Cab 5.9 Diesel

 

Welcome to the site. Check the blend doors under the dash that allow inside air to "blend" with outside air. Likelyhood it is broken and letting air in all the time

 

That would be my guess too. The door is probably lying on the fan, and is probably blocking your fan airflow. Since you now have an opening from the outside to inside, you'll be getting a draft. You have four choices..
1. Go to Heater Treater and get a repair kit, I think it's under $200 and a relatively easy fix.
2. Bring it to a dealership, the estimate I got was well over $800.
3. Block off the outside air grill to prevent any air from outside entering. This is what I did, takes about a 1/2 hour and some bloody knuckles.
4. Leave it alone.