It is located under the glove box.You will have to remove a plastic kick plate.You will see an electrical plug going into the heater vent system.Unplug and remove the 2 screws holing in the resistor pack.
It seems to be a common problem with all mopars,I have owned to others and had the same problem.Mine seemed to go atleast once a year.I know live with only high speed tired of putting money into low and med fan.