Hello everyone, new to this .. I have a 2011 f150 crew cab platinum , at times when I turn the ac on and accelerate I hear a hissing noise form under the dash on the passenger side . Anyone have a clue what this is or why it is doing it?

 

Congrats on your new vehicle.
Since it's covered by warranty, why not let the dealership check it out?
Sounds like a possible vacuum leak.

 

Definitly sounds like a vacuum leak. Commen for vehicles switches and air flow control valves to be operated by vacuum. Under warrenty take it to dealership.