I wouldn't replace anything until you find out what is really causing the trouble. This will mean you have to test some things using at least a test light probe to check for voltage. Use the probe to see if you are getting voltage to motor with the blower speed selector set to high. Check both wires going to the blower motor. If the motor is ok you should see a light turn on when the probe is clipped to ground and check each wire. If that is ok there then the trouble is most likely with the protector inside the resistor block. If that is the case you may want to have the current draw of the blower checked to see if it is excessive. You could also bypass the resistor block with a jumper wire to see if that will get the motor going. That would prove it is bad also.