Heat & Air Switch makes grind noise

I replaced the new Blower Motor with the old original one after installing the "squirrel cage" and still had the grinding noise. Next I pulled the blower motor out and temporarily installed the new blower motor without the squirrel cage. Had wife crank car and turn blower motor on while I held it in my hand with it attached electrically to the proper wiring plug.There was no grinding noise. Returned new blower motor for refund and purchased a new squirrel cage. Installed new squirrel cage on old blower motor. Success at last. The grinding noise is gone. Special Note: The old squirrel cage had a barely visible hairline crack on each side of the hole where you mount it on the blower motor shaft. My conclusion is that when we cranked the car on a morning when we experienced the extreme cold weather recently the squirrel cage developed the hairline cracks due to it being made out of hard plastic material.