Heating

Why Is My Furnace Making Noise? What Banging, Squealing, Rattling and Humming Mean

Published October 13, 2026

Which furnace sounds are normal?

Every gas furnace makes some noise. These are generally nothing to worry about:

• A soft click when the thermostat calls for heat, followed by the hum of the small inducer fan
• A quiet whoosh as the burners light
• Steady airflow from the vents once the blower comes on
• Light ticking or popping from metal ducts as they warm up and cool down

What matters is change. If your furnace sounds different than it did last winter, or a sound is getting louder week by week, it's worth paying attention — especially now, as furnaces across the Puget Sound area fire up for the season after months of sitting idle.

Furnace noises and what they usually mean

Banging or booming when the heat starts

A single loud bang just as the burners light is usually delayed ignition. Gas builds up for a moment before it lights, then ignites all at once. Common causes are dirty burners, a weak igniter or low gas pressure. This one shouldn't wait: repeated small explosions stress the heat exchanger and can eventually crack it, which is a carbon monoxide risk.

A softer bang or "oil-can" pop from the ducts when the blower starts or stops is different — that's usually ductwork flexing, often from a clogged filter or closed vents. It's annoying but less urgent.

Squealing or screeching

A high-pitched squeal often means the blower motor bearings are wearing out or, on older furnaces, a belt is worn or slipping. It may come and go at first, then become constant. Left alone, a failing blower motor can stop completely — and without airflow, the furnace overheats and shuts down.

Rattling

Rattling can be as simple as a loose access panel or screw, or ductwork that's come loose from a hanger. But a rattle that starts with the inducer fan can mean a failing inducer motor, and a rattle inside the cabinet can be a loose blower wheel. If it rattles only when the burners are on, have it checked.

Grinding or scraping

Metal-on-metal grinding is a sign of a motor with failing bearings or a blower wheel rubbing against its housing. Turn the furnace off at the thermostat and call. Running it can turn a motor repair into a bigger one.

Humming or buzzing

A low hum while the furnace runs is normal. A loud buzz — especially with no airflow — often points to a failing capacitor or a motor that's trying to start but can't. Buzzing from the control area can also be a loose electrical connection or a transformer issue.

Repeated clicking with no heat

One or two clicks at startup are normal. Clicking that repeats while the burners never light usually means the igniter or flame sensor isn't doing its job, or a safety switch keeps stopping the sequence. If the burners light for a few seconds and then go out, see our guide to why a furnace keeps turning on and off.

Whistling

Whistling usually comes from air squeezing through a tight spot: a clogged filter, a filter that doesn't fit its slot, closed registers, or a gap in the ductwork. It's often the easiest noise to fix yourself.

Rumbling after the furnace shuts off

A rumble that continues after the burners should be off can mean gas is still burning because of a dirty burner or a faulty gas valve. Treat this as urgent and call a technician.

Quick reference: furnace noise chart

Safety first: If you smell gas (rotten eggs), don't flip switches or use your phone indoors — get everyone out and call your gas utility or 911 from outside. If a carbon monoxide alarm sounds, get everyone outside and call 911.

DIY checklist: safe things to check first

These steps are safe for any homeowner and solve a fair number of noise complaints:

1. Replace the air filter. A clogged filter is behind a lot of whistling, duct popping and overheating. If you can't see light through it, change it.
2. Make sure the filter fits. A filter that's the wrong size can rattle or whistle. The size is printed on the edge.
3. Open supply vents and clear return grilles. Closed or blocked registers raise pressure in the ducts and make them pop and whistle.
4. Check the furnace door. Make sure the access panel is seated firmly. A loose panel rattles — and on many furnaces, it also trips a safety switch that stops the heat.
5. Tighten what you can see. Loose screws on the outside of the cabinet or on exposed duct joints can be snugged up by hand.
6. Listen and note the timing. Does the noise happen at startup, while running, or at shutdown? With the burners or with the blower? This helps a technician find the problem quickly.
7. Check the outside vent pipes. On high-efficiency furnaces, make sure the PVC pipes outside are clear of leaves and debris.

Don't open the burner compartment, oil the motors, or adjust the gas valve yourself. If the noise continues after these checks, it's time for a pro.

When to call a pro

Call a licensed HVAC technician if:

• You hear a bang or boom when the burners light
• There's grinding, loud buzzing, or squealing that won't go away
• The furnace clicks repeatedly but won't heat
• A rumble continues after the furnace shuts off
• The noise started along with weak airflow, a burning smell, or a breaker that trips
• You see soot, scorch marks, or a yellow or flickering flame
• The furnace is 15 or more years old and getting louder each season

A technician will inspect and clean the burners, test the igniter and flame sensor, check gas pressure, inspect the blower and inducer motors and capacitor, and look at the heat exchanger. Many noisy furnaces need a single part. If yours has a cracked heat exchanger or a failing motor on an aging unit, we'll give you honest repair-vs-replace advice — including whether a heat pump makes sense and which utility rebates you may qualify for.

Yeti Heating & Air provides furnace repair across Seattle, Bellevue, Kirkland, Redmond, Renton, Shoreline, Lynnwood, Bothell, Edmonds and Everett. Our licensed, insured technicians give you an upfront price you approve before any work starts, and we offer 24/7 emergency service if your heat goes out.

Why it pays to fix noises early

A noise is usually the earliest warning you'll get. A squealing blower motor or a weak igniter often keeps working for a while — until the coldest night of the year, when the furnace runs the longest. Fixing it on your schedule usually costs less and avoids an emergency call. A fall tune-up is a good time to have new sounds checked before winter.

Furnace making a strange noise? Call (206) 823-0670 or request a callback. We're available Mon–Sat 7am–7pm, with 24/7 emergency service.