To check the blower motor circuit, look at the fuse, connections, and battery. Connect a voltmeter to the blower motor connector and check voltage readings as you move the switch. Test the thermal resistor relay and check for continuity in the resistor block. In case it only operates at one speed, check for voltage and test for grounds. If there is no voltage, check the wiring of resistor block connector. Also, if none of this is okay, verify the voltage at switch connector and wiring too. But if your motor does not run at any speed, check into the fuse plus test for voltage at the motor connector. Inspect wiring but no voltage, or test motor but yes to voltage. Ground each terminal of the switch connector to check for motor operation.