Furnace Making Loud Noise

When this becomes an emergency

• You hear a distinct bang from the furnace shortly after each call for heat.
• There's a high-pitched whine that rises and falls with the blower.
• A scraping sound comes from inside the blower housing.
• The system has developed a hum or buzz that carries through the whole house.

What a pro does

The sound tells the tech where to start. Scraping inside the housing usually means the blower wheel has shifted on its shaft and is contacting the shroud, which is a fast fix if it's caught and an expensive one if the wheel destroys itself first. A whine that tracks blower speed points at the motor or its bearings. Buzzing that carries through the house is often electrical, a contactor or transformer rather than anything mechanical, and it gets traced with a meter. Older equipment in mid-century houses tends toward bearing and belt noise, while newer variable-speed units are more likely to whine or resonate through the ductwork.

Frequently asked questions

Furnace Making Loud Noise?

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