Air-Vent selector not working right. (Vacumm Issue?) Help!

I always have air coming from my front (panel) vents. If I switch it to floor, the air re-directs to floor momentarily and then goes back to panel vents. On defrost, it comes out of the defrost and panel. It didn't used to do this, why now? Summer time I use the panel vents for A/C, but winter is coming and I don't want hot air blowing in my face. I've got an 01' Dakota, 4.7 SLT, Club Cab, 4x4 if it helps or makes a difference. Somebody have any ideas of things to check out? I'm guessing it is a leaky vacumm line, where should I look?

Did you reslove your problem? I'm having the same problem. Thanks

Depending on model options, most are electronically controlled now (no more vacuum lines). It could be a bad AC Head Unit, Broken Mode Door actuator (or hinge), or just a faulty actuator. Best thing to do is check for ATC codes (DRB-III) - if applicable (model options come into play there), or just look under the dash and watch the actuators while someone is changing the settings on the dash.