The heater blower motor is an electric fan that provides the airflow that is directed into the passenger compartment for the heating and air conditioning systems.
The brushes in the heater blower motor can wear over time and cause the blower motor to stop working. Also, mice can build nest in the blower motor causing it to jam and malfunction. Once the blower motor quits working properly, then it should be replaced.
Most manufacturer's factory warranty cover the heater blower motor under the bumper-to-bumper warranty, if it fails due to a manufacturer defect or workmanship. There are extended auto warranties available that will extend coverage of the blower motor after the factory warranty has expired. When purchasing an extended warranty, make sure to look at which coverage level includes the heater blower motor.