Sounds like the evap coil drip pan drain holes are plugged.......pan fills up with condensate, overflows and gets carried into discharge plenum by fan.
Condensation should be running down roof.
Will need to go up on roof, remove shroud cover and then remove sheet metal cover over evap coil. Clean evap coil, drip pan & pan drain holes.
2014 Coachmen Catalina
243RBS 50th Anniversary
2013 F250 Lariat 6.7 Powerstroke