I have a 2003 3500 with Dual climate controls. For several months now the heating or air conditionar will work fine then quit blowing throught the vents and sounds like it is just blowing the air behind the dash infront of the passenger seat. If you shut it off the heater for a while sometimes when you turn it back on it will work again but it seems to be very random. I have replaced the control unit on the dash with no change. Has anyone else had this problem or have any ideas.
