My blower motor started popping fuses. Ive done some preliminary trouble shooting and need further advice.

I checked all 3 leads from the dash, and each seems to be doing what they should. Voltage at the corresponding terminal for low, mid, high. Wired the blower motor straight off of battery power and blower motor seems to be fine. No major arcing when I lite the motor?

Motor seems to run on low speed OK through the dash, but if you move the switch to med or high, it blows the fuse.

Resistor in the heater box possibly bad?

Thanks for any help.