Thanks to all who responded to my question about fan working only on high.
Everyone seems to agree it's the resistor. Now, how do I find and replace it? Chevy Prizm 2000.
Typical place to look is in the duct work near the blower motor. The air keeps the resister cool. Look under the dash on the passenger side. You might have to remove the glove box. It will have a connector with 4 - 6 wires.