Why is the furnace blower not working? The symptom narrows the next observation but does not identify a failed part. For the furnace and heating system, first separate what the thermostat or normal controls request from what the indoor and outdoor equipment actually do. Note airflow, temperature change, timing, sound, odor, visible water or ice and whether the problem affects one room or the whole home, without opening a panel or reaching into equipment.
Request a diagnosis that separates the blower assembly from its controls and airflow causes, with labor, compatible parts, and post-work airflow testing identified independently. Equipment access, electrical-code rules, parts availability, cold-weather urgency, and permit or inspection requirements vary across homes and jurisdictions. Note whether the furnace produces heat or attempts ignition without room airflow, whether the fan works in another mode, and whether there is humming, overheating, smoke, or a protection trip. A motor that never runs differs from a blower that starts late, runs weakly, or is commanded off by a control or safety condition, so avoid reaching into the compartment to test it. Service can verify the fan command, electrical supply and controls, motor and wheel condition, airflow restrictions, temperature limits, and compatibility of any replacement assembly.