do you have it on recycle or are you bringing it in from the outside? If it's outside try changing your cabin air filter. Just go to your local autoparts store and order a cabin air filter, it should be under the windsheild wiper assembly.

we have a team tech forum that works great for these questions further down the road. I made the same mistakes, no biggie you'll figure it out.

 

Could be something stuck in the motor. I had a mouse in mine, but it made one heck of a racket. The motor is located in the passenger side footwell under the glovebox.