2002 Chevy Silverado Flappin Noise under dash passenger sid

I have a flapping noise under the dash on the passenger side, it only happens when you are traveling down the road. It seems worse when there is a stiff breeze outside. I am also having problems with the recirc control on the heater controls, I can not get the unit to switch to outside or recirc, the light blinks but will not stay lite in either position. Can you help please?

Thanks,
Dave