In 1948, the first of the F series trucks with a one-piece windshield hit the assembly line. Over the years several models were introduced including the custom model. In 1993 the custom model was dropped in favor of the XL model. The blower motor resistor works in conjunction with the fan switch to regulate the speeds of the fan. The resistor on early model vehicles is a series of three coils of wires, each of a different resistance used to regulate voltage. All late model vehicles use a solid state resistor. Both resistors, early and present, have one common problem -- heat, which governs their useful life span.
Open the glove box. Remove the screws from the glove box liner with the screwdriver. Pull the liner out.
Pull the four-wire electrical plug out of the blower motor resistor. It is located just to the left of the blower motor.
Remove the two 7 mm screws in the resistor using a socket driver. Pull the resistor straight out of the module.
Insert the new resistor and tighten the two screws snugly. Plug the electrical harness connector into the resistor. Install the glove box liner and tighten all the screws snugly.
