The blower resistor unit in your 2002 Jeep Grand Cherokee controls the blower speed in your HVAC (Heater-Ventilation-Air Conditioner) system by varying the resistance of the blower motor circuit. As resistance goes up, the blower speed goes down. The normal default, if the resistor fails, is to supply full power to the blower so that it runs on high speed only. However, this resistor is a solid-state design that may not supply power to the blower motor at all when it fails.
Open the glove box and remove the plastic door limiting strap, on the right side of the glove compartment, by pulling it toward you and then out of the hole it is snapped into. Unsnap the right-side and then the left-side glove compartment hinge from the hinge bar, using a screwdriver to pry the hinge as necessary, and set the loose glove compartment aside.
Unplug the wiring connector from the blower resistor, located on the center on the evaporator case to the left of the blower motor housing. Remove the two Allen-head screws, using an Allen socket from the socket set, that attach the blower resistor to the evaporator case. Slip the resistor out of the case.
Install the new resistor into the evaporator case and tighten the Allen screws securely. Examine the electrical connector. If the connector is melted, replace it with a new connector, available from the manufacturer, by cutting the old connector off with a pair of wire cutters and splicing in the new connector using butt connectors. Plug the electrical connector into the resistor.
Check the blower motor function by turning the key on and moving the speed selector switch through its range. Snap the glove compartment back into place and reconnect the door limiting strap.
