On a 2002 Mazda Protege why would the fan only work when the fan knob is set to 4?

I had the exact problem with mine 02 Proege and the issue was there is a resistor that controls the fan speed and when the resistor blows it only gives full current(better than no current) to the fan. I took mine to the dealer and they charged $60 to fix it, parts and labour. cheers the problem IS the resistor, i have no doubt. usually resistor are located under the dashboard on the passenger side. $60 dollars is expensice, the part im sure costs no more than 10 dolars, try to change it yourself, its basically a plug that you plug in.