After not receiving a accurate response from the experts on this website, I did my own research on this problem. After many calls I finally talk to a HVAC design engineer at Mitsubishi Motors. According to Mitsubishi Engineer, if the blower fan only operates on the highest speed setting, or is missing one or more speed settings below that, most likely the blower resistor has failed. The part is not known as a blower resisitor in the technical manuals. It is known as a heater resistor. The resistor is located on a separate wire connection and mounted on the air exchange unit with resistor half of the unit inside of the air exchange.