blower control knob doesn't work in one of the positions

blower resistor is bad. under the right side of the dash. Roy

Yes, Roy is correct, it is most likely the blower resistor. Ours did the same thing, we let it go and just used different speeds. Unfortunately, our blower control switch melted. When I replaced the resistor, it appeared that something on it possibly shorted to burn out the speed selector switch. I recommend taking the 30 minutes and replacing the resistor before this happens! Much cheaper and easier than having to also replace the speed selector switch.