Depending on the year, the reistor can be found on the passenger side, under the dash. Remove the glove box, and you will see the resistor. Remove and reinstall.
Disconnect the negative battery cable from the battery. Disconnect the electrical connectors from the blower motor. Remove the radiator coolant collecting bottle from the right side of the engine compartment.
My heater blower stopped working--only ran on "high". Part of the problem was a blown resistor block; this device is bypassed if the thermal cut-off switch on the block overheats.