When it comes to trying to test a blower motor, there are a few options.
First, you should use the “crosswalk method”. Stop, look and listen.
If you hear a humming sound, this could be the motor windings locked up. After you take the blower door off to look, however, there is a door safety switch. (black button in the center of the furnace on the right or left side usually). You will need to depress this or tape this down to get power to the unit with the door off.
Next, you can look to see if the wheel is spinning. If not, you may be able to carefully reach in and manually turn the wheel and get the motor to start. If this is the case, I would replace the capacitor (pictured above) and see if this does the trick.
Generally, if the capacitor goes bad to the point that the motor doesn’t spin, the damage has already been done, and would be best to replace the motor and capacitor. Just be sure to get the correct size to match your new motor. It may not be the same size as your old capacitor.
If you have an electrical meter, you can test the power coming from the control board at the heat or cool connection for 120 volts. If you do, then your motor is likely bad. If you do not have power, you could have a bad control board.
Another way to check your blower motor would be to turn the power off to the furnace and unplug the heat or cool wire from the control board, unplug the door switch (shown above) wire that runs to the L-1 connection on the board and plug the blower motor wire into the door switch terminal instead. Then turn the power back on. This will put 120 volts directly into the motor and start it automatically if it is working. If nothing happens or you only get a humming sound, the motor is bad.
