Furnace blower motors are designed to blow the heat generated by the furnace's heat exchanger toward the duct system. This motor is activated by either reaching a preset time, or by sensing that a specified temperature has been reached.
When the motor blows the air over the heat exchanger, the air is heated to the desired temperature. Once the heated air reaches the duct, it's sent to the various vents in the system. These air vents allows the heated air to be distributed into the building's living space.
The home's thermostat will determine when and if the desired temperature of the home has been reached. Once this temperature is achieved, the thermostat communicates to the furnace. This communication leads to the temporary cessation of the hot-air-producing process. When the thermostat indicates that the desired temperature is no longer achieved in the home, a message is sent back to the furnace to begin operations once again.
The blower motor is an integral part of the furnace's heating ability. If the blower fails, the heat produced by the furnace cannot be transferred to the duct system and warm air will not be distributed throughout the house. This will lead to the thermostat continually messaging the furnace to begin hot air production and wasteful energy consumption.