Furnace starts and stops with a loud click but blower never comes on; heat exchanger gets very hot.

Safety first: Turn off power immediately to avoid overheating and potential heat exchanger damage.

• Check blower wheel movement: With power off, spin the blower wheel by hand. If stiff or stuck, the motor bearings may be seized and the motor must be replaced.
• Inspect capacitor: Locate the blower run capacitor. If it is bulged or leaking, replace it with the same microfarad and voltage rating.
• Check for belt (if applicable): On older Fraser‑Johnston furnaces with belt‑drive blowers, inspect the belt for breakage or slipping. Replace and tension correctly.
• Professional service: If the motor hums but does not start, or if the relay is not sending power, a technician should test and replace components as needed.