I don't quite understand the relationship between the resistor and the fan motor. It appears the motor is on high when the resistor is bypassed, medium and low through the resistor. Assuming that's true, how can I determine if the motor is at fault or the resistor is at fault (seems to run on low speed only). Possibly wire the motor directly to the battery and see what happens?? Or could the switch be at fault?? I do see a faint spark when moving the switch between positions but that may be normal. This is a '62 without A/C (blower motor has a single wire to it).