I've got a 2009 Impreza.

 

No matter how I set the vent switch, air comes out at the windshield vents and never comes out of the center dashboard vents.

 

The recirculating feature turns off when the switch is set to any setting that includes the windshield, as it should– but there's always air coming out the windshield vent, and that shouldn't happen.

 

Air does come out of the side dashboard vents when I set it to dashboard vent.

 

I'm still under warranty, but I'm just wondering if there's some trick to getting it to work that I'm missing. I'd hate to bring it in to find that I forgot to press a button or something.

Nope. One or more of the flaps is stuck. Take it in.