Blower not Blowing

I have a 97 Suburban, when I try to turn the heat/ac on, nothing blow out of the vents from the dash, but if I turn on the rear heat/ac, it comes on. My rear defrost works, the recycle button works also. Just nothing comming out of the front dash vents. I checked the blower fuse and it looked good. I'm stuck, what could it be? Any ideas?:confused: