Furnace Making Strange Noise
Quick Answer
Furnace noises usually indicate specific problems: banging = delayed ignition, squealing = belt/motor, rattling = loose parts, rumbling = dirty burner, grinding = bearing failure. Some noises are minor, others require immediate attention.
Safe Checks You Can Do
- 1Tighten access panels - Loose panels are the most common cause of rattling. Secure all screws.
- 2Replace air filter - A clogged filter can cause whistling and make the blower motor strain.
- 3Check ductwork - Loose duct connections can rattle. Secure with foil tape if accessible.
- 4Clear debris - Check around the furnace for any objects that could be vibrating against it.
Noise Types & Causes
- Banging or booming
Usually delayed ignition - gas builds up before igniting. Can be dangerous. Call a pro.
- Squealing or screeching
Often a slipping blower belt or dry motor bearings needing lubrication.
- Rattling
Loose panels, ductwork, or internal components. Check screws and connections.
- Rumbling
Dirty burners or a pilot light issue. Burners may need cleaning.
- Grinding
Motor bearing failure. Turn off immediately and call for service to prevent damage.
When to Call a Pro
- Loud banging when furnace starts (delayed ignition)
- Grinding or metal-on-metal sounds
- Squealing that persists after checking belts
- Any noise accompanied by burning smell
- Noises getting progressively louder
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