WHAT IS THAT LOUD NOISE COMING FROM MY FURNACE?
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Some furnace noises are normal, including a low hum, the sound of air moving through the vents, and occasional popping as the ductwork expands. However, loud, repeated, or persistent banging, scraping, rumbling, rattling, buzzing, hissing, whistling, or clicking may indicate a loose component, restricted airflow, an ignition problem, or a failing motor.
Turn the furnace off and contact an HVAC professional if the noise is severe, begins suddenly, or occurs with smoke, a burning odor, or no heat. If you smell gas or your carbon monoxide alarm sounds, leave the home immediately and contact the appropriate emergency service.
If you’re wondering, “Why is my furnace making a loud noise?” read on to learn the answers!
Common Furnace Noises and What They Mean
Furnace noise | Possible cause | Recommended action |
|---|---|---|
Scraping or screeching | A damaged blower wheel, fan blade, motor, or motor bearing | Turn the furnace off and schedule an inspection. |
Thumping | An unbalanced blower wheel or motor | Have an HVAC technician inspect the blower assembly. |
Banging at startup | Delayed ignition, dirty burners, or a loose or broken component | Turn the furnace off and call for professional service. |
Rumbling | Normal burner operation if brief, or a burner problem if unusually loud or persistent | Schedule service if the sound continues after startup. |
Rattling | A loose panel, fastener, duct connection, or internal component | Tighten an accessible exterior panel only if it is safe; call a technician for internal rattling. |
Popping | Normal duct expansion or restricted airflow from a dirty filter or closed vent | Check the filter and vents. Have persistent or forceful popping inspected. |
Buzzing | A loose component, failing capacitor, motor problem, or electrical issue | Turn the system off if the buzzing is loud or persistent and schedule service. |
Hissing or whistling | A clogged or incorrectly sized filter, blocked vent, airflow restriction, or duct leak | Check the filter and vents; arrange a duct or furnace inspection if the noise continues. |
Repeated clicking | An ignition, control board, relay, or electrical problem | Schedule professional service, especially if the furnace does not start. |
MY FURNACE IS MAKING A SCRAPING NOISE
Let's just say scraping sounds are not good sounds when they're originating from your HVAC. A scraping noise usually means something is wrong with the fan blades and/or motor. If you hear something that sounds like screeching or scraping, turn off your heating equipment right away. A foreign object may be obstructing your blower, or one of the fan blades may be warped or broken. In either case, it can cause your motor to burn out. You'll need to call a technician to inspect your furnace and correct the problem.
MY FURNACE IS MAKING A THUMPING NOISE
Things that go thump in the night or any other time mean something is out of balance. Thumping sounds that come from your furnace could indicate that a motor or blower wheel is out of balance. This could cause big problems for your mechanical equipment down the road. It's best to have an HVAC professional take a look and fix a small problem before it becomes a big one.
MY FURNACE IS MAKING A BANGING NOISE
If you hear extremely loud banging sounds, shut the heating system off – something most likely has broken and disconnected. A banging noise when the furnace turns on, followed by no hot air, is often a result of dirty furnace burners letting gas accumulate in the furnace before the gas ignites. The delayed ignition from the gas buildup is what causes the loud bang. It is important not to ignore this noise. Doing so can crack your furnace's heat exchanger, which oftentimes results in the need for a new furnace.
MY FURNACE IS MAKING A RUMBLING NOISE
A low rumble is a normal sound when your gas or oil-fired furnace kicks on. However, if that rumble is louder than usual—or lasts longer than usual—this could indicate a very serious problem with your burner. If you hear a loud or long rumbling noise coming from your gas or oil furnace, turn off your equipment and call for service.
MY FURNACE IS MAKING A RATTLING NOISE
A rattling noise coming from the furnace could mean that the fasteners to the metal housing of your heating unit have worked loose. That's not usually a serious issue, and those fasteners can be easily tightened. However, if the rattling noise is coming from inside the unit, that's another matter altogether. You should call a technician to see if the problem is serious.
Sometimes twigs and other outdoor items can get inside the fan of an outdoor unit, causing a little clanking or rattling around. If you can see this is the problem, you can just switch off the power and remove the debris. If you see that the debris has somehow caused damage to the compressor or fan, call a technician.
MY FURNACE IS MAKING A POPPING NOISE
Popping sounds are quite common when you turn on your furnace at the beginning of the heating season. When your furnace blower starts, it sucks in air and blows it out through supply ducts. This causes different parts of your ducts to contract and expand. This is usually the sheet metal in your ductwork responding to pressure — popping one way in reaction to the negative air pressure of the fan, then popping back when the fan shuts off and the pressure releases. A minor popping noise is natural and not usually a worrisome noise, loud or persistent.
However, when there is a loud pop or bang, there could be a more serious problem caused by undersized ducts, closed vents, or a clogged air filter. In that case, you should have your ductwork inspected.
MY FURNACE IS MAKING A LOUD BUZZING NOISE
If your furnace is making a loud vibrating or buzzing noise, this typically indicates that some aspect of the system is loose. If you notice any loose fasteners, you may be able to fix this issue, but for a full diagnosis and repair, you'll want to call for service, especially if the buzzing seems to be coming from the inside of the furnace.
MY FURNACE IS MAKING A HISSING NOISE
If you're hearing a hiss, you're likely hearing escaping air. This could be caused by an improperly installed air filter or one that is the wrong size. Often, having too many closed vents or having furniture blocking airflow can be the cause of a hissing sound. If the hisses become very loud, it could indicate there is a leak somewhere in the ductwork — and that means a lot of expensively heated air is escaping where it can’t be used. Again, if this is the case, you’ll want to have your ductwork inspected.
MY FURNACE IS MAKING A WHISTLING NOISE
Whistling noises coming from your HVAC equipment could mean there's a refrigerant leak in your condenser or some other problem that is causing internal pressure. If you hear a whistling sound coming from your furnace, call for a service technician.
MY FURNACE IS MAKING A LOUD CLICKING NOISE
Repeated clicking noises often indicate that there is a problem with your furnace's ignition system. Your furnace's spark igniter is trying to ignite your pilot light, but is failing to do so, resulting in your furnace not starting.
To check whether an ignition switch malfunction is causing your furnace problems, determine whether your furnace has a pilot light or an electric ignition, then light the pilot to observe the ignition process and make sure it is functioning normally.
WHEN SHOULD I WORRY ABOUT FURNACE NOISE?
Heating and cooling units are mechanical equipment, which means they make noise. Not all that noise is bad, and the occasional strange noise may merely indicate that it's time for a tune-up. However, any loud, disruptive, or continual noises usually mean there's a real problem, and you should contact a trusted local HVAC company like A.J. Perri to come and take a look.
Contact A.J. Perri for Full Gas Furnace Repair & Installation Service
Heating and cooling units are mechanical equipment, which means they make noise. Not all that noise is bad, and even the occasional strange noise may merely indicate that it's time for a tune-up. However, any loud, disruptive, or continual noises usually mean there's a real problem, and you should contact a trusted local HVAC company like A.J. Perri to come and take a look.
The local HVAC experts at AJ Perri are ready to assist you with any loud furnace noises or other home HVAC needs 7 days a week! Call us for expert service and get your furnace back to working without all the loud noises. Our trained heating technicians will be able to tighten and lubricate parts, replace belts and filters, and provide the solution to small problems before they become big repairs — or possible dangers.
