hvac & A/C vent issue

[ofatmikeo]

ok so my heater / ac works great but when under acceleration only the defroster vent works . even if I have the selector put to dash or floor the air flows out of selected vent . as soon as I step on the gas pedal it switches back to the defrost (windshield vent) weirdest problem I have ever found . any ideas on where to start looking or has anyone else had this issue ? iits a 99 ram 1500 quad cab with the 5.9 auto trans ???????

 

[KenBerry]

A very common issue. You'll find lots of threads if you search for "wild vents" or "crazy vents"