The blower motor resistor is in the rheostat located within the fan switch itself. The switch has a constant power source that internally controls the 'resistance' to slow down or speed up the fan depending on what setting you have it on.
Before replacing the switch, it is best to do an electrical test on the wiring to make sure the switch is failing. It may not be getting power, indicating perhaps a blown fuse or another electrical issue.
-Ben from MechanicsCentral.com
Posted on August 28, 2012