defrost now blowing out front vents...

[stickyfinguhz]

so i recently turned on just my defrost button, it worked on my windshield but there was clicking noises behind my steering wheel. so i go today and the clicking stopped but now when i put defrost on it doesnt come out the vents by my windshield but the vents on the dash above the stereo and a/c buttons n stuff. it is really hot air but the clicking has stopped. but nothing is coming out by my windshield.. anyone know what could be causing it to switch to a different vent?