I got a 2003 Chevrolet s10 blazer no heat blows on the floor but got on defrost

Sounds like a blend door operation problem. Try cleaning the blend door, lubricating it with WD-40, and checking out the blend door actuator's operation. Remove the actuator and turn the ignition switch on and off. Make sure that the actuator's shaft rotates as it should. If it doesn't, install a new actuator--the plastic gears inside can jamb or break.