Need help with 73 duster heater fan problems

I have a. 73 duster, ac car but not hooked up. My heater fan switch does not work unless I take the resistor out and put the coils together on the resistor. This tells me that something is messed up back through the system. Could it be a bad fan switch or something else. I think the fan switch is the only thing between the fan motor and resistor.