The blower resistor heat sink sits in the main vent coming from the blower. As the blower is set to a lower and lower speed the unit gets hotter and h otter absorbing the energy the fan is not using. At slower speeds there is less air flowing over the heat sink to absorb the additional heat and so at any fan setting below 6 the unit becomes hot enough to fry the electronics . The solution is to "never" run the fan below 6