Heater/Air Conditioner Blower

I have a 2000 Ford Taurus SES. My heater - A/C blower stopped working. I replaced a fuse in the Fuse box under the dash (which according to the Owners Manual) was the blower fuse. However this Just gave me high speed blower. I do not have a low or medium blower speed. I have checked every other Fuse I know to check, both under the dash and under the hood. They are OK. What could I check Next? Or what might be causing my Problem? This is my First Post Thanks.