This could either be a faulty switch or a faulty resistor. To test the switch you can unplug the conector from the switch a use a short bit of wire to bridge the terminals, if the fan fan works its the switch. If the fan still works on full speed only it will be the resistor, which is located in the left side of the heater box, its held in a couple of screws, just follow the wires to it.
Run-Rite Vehicle Services, March 2005
