As many others have posted, when accelerating air switches from the panel vents to the defrost vents. I've read numerous times that it may be the vacuum check valve. I've attached a picture of what I believe to be the check valve. This valve should be a one way valve where air passes only one way. When I blow through both ends, air passes through both ways. Can someone please confirm if this is the check valve.

This is from a 2002 F-150 XLT 4.6L 2WD

Thanks in advance.

https://www.f150online.com/forums/me...-09-30-345.jpg

 

Bump...Anybody...Please

 

Link goes to a blank page.

 

Maybe becaue I had it marked as private. I marked it as public, hopefully this helps. Is there a better way to add pictures?

 

I guess I should have re-added the link. Hopefully this works.