So the Broan bathroom fan, that I replaced about three months ago, has suddenly stopped working. The fan motor hums and gets warm, but the squirrel cage fan does not rotate. I can rotate the motor shaft by hand, and the fan spins freely, but the motor drive is not rotating the fan. Any ideas on the problem and how to fix it? Unfortunately, I had already discarded the packaging and receipt from Lowe's, so I cannot return the unit.