I tend to remember there is some sort of relay under the dash on the passenger side that controls a valve/vent to open to allow the a/c to work properly.

Currently, I have a Dodge Ram 1500 - Year 2001 that is blowing hot air on the right hand vents (3 vents to the right) and colder air on the left 2 vents (driver side). Anybody got an idea on this one?

THanks!

Several complaints on google about this.

The blend door on the passenger side is stuck

Says the repair is very involved...

Do a search on google for tsb 24-004-03. Click on second link.