What stops a blower motor from working?

A residential indoor air handler blower motor can be stopped by several electrical, mechanical, and safety control failures. A frequent electrical culprit is a blown low-voltage control fuse on the furnace control board or a tripped main circuit breaker that cuts power to the unit. Mechanically, worn-out motor bearings can seize up and prevent the shaft from spinning, or a failed run capacitor can rob the motor of the electrical torque needed to start. Additionally, safety mechanisms like a clogged condensate drain float switch or an internal motor thermal overload protector will shut the blower down to prevent flooding or fire hazards when components overheat due to a severely restricted, dirty air filter. You can troubleshoot by checking fuses, testing capacitors, and replacing dirty filters. You can verify resolution when the blower motor spins freely.