Denny,
When the switch is all the way up it is in the off position (I'm sure you already know this). Then there are 3 detented positions for High, Medium, and Low. The first detent down is for high. The resistor is bypassed and the full voltage is applied to the heater motor. In this position the switch should not be any warmer than the wires carrying the current to the motor. The second detent down is for the medium speed. This connects to the center tap of the resistor and only half of the resistance is used to drop the voltage being applied to the motor. The third and last detent is when the switch is in the full down position. This switches in the full resistance of the resistor to drop the voltage further before being applied to the motor for the low speed. The switch will get warm from the heat given off by the resistor, but it should not get to the point of being hot enough to burn your fingers. It is the resistor itself that gets very hot (only in low and medium speeds) and should not be touched.
If the switch gets too hot to it has to be coming from internal resistance in the switch itself. This can be caused by corroded or tarnished contacts, loose rivets, and poor contacts in general. I have all of these conditions in my switch and have disassembled it for cleaning, repair, and rebuild.
