Will not stop blowing air out of floorboard vents

[Dhale24]

So today my 2003 pathfinder se. It was fine this morning and fine after work until I got home turned the car off was home for about 20 minutes then went to go somewhere turned the heat on then went to turn it off. The screen turns off displaying what temp and all that, it goes black as it should but air switches to the floor boards on full force and does not stop. Anyone ever had similar problems? What do I do? Where should I start

Edited February 19, 2015 by Dhale24