1997 Chevy pickup the blower on ac blows on high only does nothing on lower settings have change the blower motor but did not help?

I think you should look at your fuse panels and see if you have a blown fuse . Some vehicles have a fuse for high and low blower speeds. Your problem is either the blower motor switch itself or a defective Blower Motor Resistor Pack. More than likely the Resistor Pack is defective.