The blower resistor drops voltage to the blower making the blower operate at a slower speed. In normal operation, this resistor will be quite warm. When the heater is first installed, small amounts of smoke may be detected as the resistor coatings are first heated.
A failed resistor will result in no operation of the blower in the lowest speeds. This failure can also result in a "growling" of the blower during low speed operation.
