This is not a duel system when the AC is on the air is blown stronger and colder on driverside vents when I say colder I mean at least 20 deg, difference
Air Conditioning not working on passenger side vents on 2003 Dodge Ram 2500
There are flaps that control the airflow to the vents, the control system or the flap may be having a problem and will need to be checked out.
Is this something that a do it your self person can do? or should it be taken to mechanic?
Got the same problem and took apart the dash to look at the stuck flaps and could not figure out how to fix it myself so gave up and put it back together. This is a dealer fix if you ask me