I have a '00 intrepid, I love my car, about two months ago I turned the heater on and it worked fine, later that day I turned the heater again but no air was blowing from the front vents, there was air only blowing from the vent on top of the dashboard and has not changed since then, I turn the knobs to cool, hot, feet, front, defrost, and it still blows air from the same place. Anyone has an idea of what could it be?

Thanks.