No air blown out on dashboard in 02 Jeep Grand cherokee?

Please help. I have a 02 Jeep Grand Cherokee, but a few month ago, air stopped blow out from dashboard no matter what position and level I put the air vent control. However, air does come out from the top defrost vent, and it does come out cold air if I put AC on or hot air if I put heat on. It's just not coming out from the front dashboard. I can deal with Winter time, but in this hot Summer, I have to put AC on it's highest level, and let cold air out from the defrost vent, and I will still be sweating. I checked all fuses, and they are fine. What problem could it be? and can I fix it myself? Thanks a lot for any information and help.