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Serving Maryland and Washington, D.C.

Serving Fairfax and Loudoun Counties and the
surrounding area

Monday - Friday 7:30am - 5:30pm | Saturday 8:00am - 1:00pm. CALL FOR EMERGENCIES


Serving Maryland, Virginia,
and Washington, D.C.

Serving Maryland and Washington, D.C.

Serving Fairfax and Loudoun
Counties and the surrounding area

24 Hour Emergency Services, 7 Days a Week


B&B Air Conditioning & Heating Service Blog

What’s That Odd Sound From My Furnace Mean?


As furnaces start to go to work in the fall weather, it’s a good time to remind our customers and customers-to-be about the warning signs that can indicate it’s time to call us for Annapolis, MD furnace repairs. There are several different categories of warnings that a furnace that not all is well, and in this post, we’ll look at one of the most common: odd noises.

If you’ve lived with your current furnace for at least a year, you already know the standard noises it makes as it runs. You can expect to hear a whoosh as the burners ignite, clicking noises from the ignition system, and the whir of the blower as it sends air through the furnace and into the ductwork. You might also hear an occasional rattling from the ducts, which is the sound of the temperature change causing the metal to expand. 

When other noises start to interrupt the usual ones, you may have a problem that requires professional repairs. We’ve listed a few common trouble noises below. When in doubt, always call the B&B team to handle diagnosing the issue and seeing what work we can do. Amateur repair attempts can be dangerous!


At the simplest, a rattling noise can mean the door to the furnace cabinet was not latched properly. Try closing the door again to see if this stops the noise. This rattling noise may also mean parts of the furnace are shaking loose from the movement of the blower fan, and these can be serious problems if they aren’t corrected. 

Continual Clicking

You can expect some clicking sound from the electronic ignition system, but you shouldn’t hear clicking as a consistent noise. The sound can come from various sources. It can mean the ignition system is faulty and the burners aren’t igniting. It can also be caused by problems in the electrical control board, such as faulty relays. It might even indicate a cracked heat exchanger in an older furnace, and this is a major problem you’ll want inspected right away.


When the gas jets of the burners ignite at the start of a heating cycle, you’ll hear a small whoosh noise. This is normal. If you instead hear a startling boom sound, it likely means that the burners have delayed ignition. Too much unburned gas has built up in the combustion chamber, and when the burners do ignite, the excess gas will create a small explosion in the furnace. You don’t want either this or delayed burners (they could be dirty), and we recommend calling us for repairs. 

Clanging and Banging

Startling mechanical noises are probably coming from a loose part in the blower, a misaligned blower fan, or a bent blower fan blade. Letting this go without attention from professionals will lead to extensive damage to the furnace. 

Mechanical Shrieking and Grinding

These are the noises of motors in trouble. Shrieking means motor bearings are wearing down and will soon lead to the motor burning out if the bearings aren’t replaced. Grinding usually means a motor has burned out and will need professionals to replace it.

Trust B&B Air Conditioning & Heating Service when you need fast and effective heating repair. We are always there when you need us.

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