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While a furnace blower can keep your home warm and comfortable during the winter, sometimes it can become a noise nuisance.
Although it’s normal for your furnace to produce a sound while working, it should be fairly unnoticeable.
Therefore, when you notice any loud popping, rumbling, rattling, or scraping noise from your furnace, you should repair it immediately.
Below are different ways on how to quiet a noisy furnace blower.
What Is a Furnace Blower?
As its name suggests, a furnace blower is a component in your furnace whose main purpose is to blow hot air through the ducts into your house.
A furnace blower consists of a blower motor and a blower fan, but they are altogether known as the blower.
In most cases, the noise problem or mechanical problem you will experience is with the blower motor.
Upon starting, the furnace is forced to create hot air. An electric furnace uses electricity to generate heat, while a natural gas furnace uses natural gas.
The warm air is produced in the heat exchanger. A mechanism is required to send the air through the air ducts and into the respective rooms in your home.
That is where the furnace blower comes in. The furnace blower motor turns the fan sending warm air into rooms in your house.
If you have a single-speed blower motor, it will operate until the thermostat reaches the desired temperatures. The motor will operate at different speeds for a variable speed, allowing you to save energy.
Furnace Noises and What They Mean
If you notice sudden and unusual noises you’ve never experienced with your furnace, especially when it runs or stops, they cause concern. The main types of furnace noises that indicate a problem include:
- Repeated clicking
- Loud bangs or pops
If your furnace completes a cycle and then produces loud rumbling sounds through the house, then this should be a cause for alarm.
The fuel likely continues to burn in the combustion chamber even when the burners are already shut down. This is an indicator with the pilot light, burners, or flame sensors. You should fix this problem as soon as possible because it significantly increases the risks of carbon monoxide poisoning.
If you notice your furnace makes unusual grinding noises while it runs, this indicates that the furnace blower bearings are worn out to the point of no return-simply you need replacement. It could also indicate that the belt tension has stressed the system.
Fixing the problem as soon as possible will save you in repair. Failure to fix the problem can cause more damage to the furnace components, resulting in costly repairs.
Bumping or thumping sounds similar to those noises produced by an unbalanced washing machine often indicate a problem with the unbalanced furnace blower motor or wheel.
This problem requires immediate HVAC repair as the blower motor and wheel are important components of your furnace.
Squealing and Humming Noises
Squealing noises are also an indicator of a problem with the furnace blower motor. In most cases, a loose belt is the main cause, but the issue could be within the blower motor in rare cases.
A low humming noise is normal when the furnace runs. However, if there’s loud humming noise during a cycle or the humming noise is loud than usual, the problem could be with the fan or the capacitor.
Rattling and Clicking
If you notice rattling sounds coming from the inside of the furnace, it indicates a problem with the blower motor.
In the long run, the weight or the clips that keep the blower motor in place can become loose, or debris can collect under the wheels.
This causes the unit to shift and become unbalanced, resulting in rattling noises.
If you’re dead sure that the rattling noise isn’t from the blower motor, then a piece of scrap or possible a screw may be dislodged inside the unit.
Common loose parts that could be the cause of the furnace rattling sounds include:
- Worn blower motor fan for older furnaces
- Connections around the ductwork
- Blower motor bearings
Rattling noises could also be an indicator of a cracked heat exchanger. In this case, you will hear high-pitched rattling noises when the unit turns on. this causes the heat exchanger to leak
In most cases, homeowners often say describe the clicking noise as the sound the furnace switches make as they cycle between on and off.
A problem with the furnace can cause it to cycle between on and off too often such that the clicking sound becomes troublesome.
There are other causes of clicking sounds- it could be that the internal components of your furnace have shifted and are in direct contact with each other.
Loud Bangs and Popping sounds
Banging or popping sounds when the unit begins a cycle. This is attributed to the warm air causing the cold metal ducts to expand, and that’s normal.
However, when the popping sounds are louder than usual, that indicates that the gas furnace burners could be dirty. This causes gases to accumulate and could create a crack in your heat exchanger, requiring immediate professional intervention.
If you notice flapping noises when your furnace cycles, this could indicate that something is sucked up through the air intake and is stuck inside.
Solving this problem requires you to enter the furnace system. The problem should be solved as soon as possible.
Normal Furnace Noises
Besides the worrisome noise a furnace makes, there are other types of noises that are completely normal for any type of furnace.
As the furnace begins a heating cycle, most people notice some noises. This is not something that you should worry about. And the most likely reason you notice the noise problem is because the unit wasn’t on moments ago.
At other times, there’s a click or pop sound as the furnace starts up and then settles as the heating stabilizes. This type of noise shouldn’t worry you- think of it as the type of noise you hear when you turn on your burner stove.
In addition, old furnaces will always be louder than new models. Modern furnaces are designed with special sound insulation to help dampen the sound produced as it runs.
Additionally, if you have a variable speed furnace, you are less likely to hear the slight adjustment the unit makes compared to the single speed furnace system.
How To Quiet a Noisy Furnace Blower DIY
There are different techniques you can implement to make your furnace blower quieter. Some of these techniques are quite easy such that an average homeowner can accomplish while others require professional intervention.
Adjust the Fan Speed: Upon installing your HVAC system, the company responsible for the installation should have set the fan speed to work in line with the type of furnace you have, depending on the size of your home.
In some cases, this doesn’t happen. The fan may be too fast, which could be the source of the problem, or the blower could be pushing too much air into the duct system resulting in humming noises.
Adjusting the fan speed can help eliminate the noise from your furnace blower.
Oiling the Blower Motor: use 3-in-1 motor oil to lubricate the blower motor axle. Note that some blower assemblies have removable plastic cops on each end. Remove them and squirt a few drops of oil into them.
Below is a video on how you can oil your blower motor. However, note that the guy in the video did it wrongly- just forward the video to about 6:30, and you’ll see the caps that need to be removed.
Replace the Bearing: in the long run, the bearings in the fan will wear out and begin to fail. This results in unwanted noises, and replacing the fan bearings can help eliminate the excess noises.
Inspect the fan blades: even though it happens in rare cases, the fan blades can bend. This results in unwanted noises from your furnace blower.
Deep cleaning the fan helps eliminate dust build-up. Too much dirt builds up, causes loud and irritating humming noises.
Motor replacement: if your furnace blower motor is producing some loud knocking sounds, this could be an indicator that the motor needs to be replaced. This can be an expensive fix but a must to ensure that your HVAC is functioning properly.
Insulation: motors generate noises even when properly lubricated and operating well. Insulation is a great way to dampen noise coming from the furnace blower. You can use acoustic panels or soundproof blankets and attach them to the outside of the furnace cabinet to help dampen the noise.
Belt Inspection: the belt on the motor can crack, break or become frayed. Replacing worn-out belts will help eliminate belt whining sounds.
Motor Mount: because the motor axle continuously spins the axle, the mountings can become loose, resulting in unwanted noise. Inspect around where the motor is mounted and tighten any loose mounts.
Inspect the Filters: dirty and clogged filters will cause humming and whistling noises. Clean or replace the worn-out filter for an efficient and quiet operation without putting too much strain on your HVAC.
Use Acoustic Sealant: Use acoustic compounds such as green glue to fill in all the gaps present in the duct system. This will significantly reduce the noise and make the duct system more energy efficient.
Inspecting and Fixing Noisy Furnace Blower
Since there are several reasons to make your blower produce an unusual noise, you must approach them differently.
You can approach them by fixing the furnace itself, the furnace room, or both.
These problems may arise from faulty blower motors, damaged blower wheels, dirty air filters, leaky ducts, damaged or loose blower belts, dirty burners, faulty heat exchangers, and more.
Since they are hard to ignore, here is how you can detect and fix your noisy furnace.
A Faulty Blower Motor
A loud squealing, knocking, whirring, or clunking noise from your furnace blower may indicate a faulty motor.
To eliminate these sounds, ensure you lubricate the motor regularly. Lubricating reduces the noise while keeping the motor performing optimally.
Even better, you reduce repair costs and keep running for longer when you detect the issue early.
However, lubricating your motor requires skill and knowledge since you must remove it.
For that reason, I recommend you look for a professional technician to do it for you.
They inspect your blower’s motor, advise you accordingly and repair other parts if need be.
A Damaged Blower Wheel
Sometimes your furnace blower might produce a clanking or scraping sound, indicating two metals are grinding against each other.
In most cases, this issue is serious and commonly comes from your blower’s wheel.
When you hear such noises, chances are, your furnace’s wheel is loose, making it grind against your blower’s casing.
In such cases, treat a loose wheel as a serious issue and fix it immediately.
If you continue running your blower, it might increase the damage and cost more cash to repair.
Although simple lubrication may do the trick, opening the wheel requires expertise.
Therefore, we advise you to switch off your furnace blower and call a professional HVAC technician to make a complete diagnosis.
Loose or Faulty Blower Belt
This problem usually arises from furnaces using belt-driven motors.
Here you find that the blower might start producing a squealing sound due to a loose belt.
In addition, a dry bearing shaft or other moving parts may produce a squealing noise too. The solution, in this case, is to lubricate or replace the moving parts for the long run.
Even if it might seem possible to replace them yourself, I advise you call a qualified technician.
Here, you get to learn the issue and specific solutions while the technician does all the necessary repairs on your entire system.
Sometimes during your furnace’s operation, its burner may start making a loud rumbling noise indicating dirt build-up.
In most cases, the dirt comes from dust or soot, clogging your furnace’s airflow.
Once you start hearing the noise, take immediate action since it indicates delayed ignition. Delayed ignition is dangerous as it can cause gas build-up, leading to an explosion.
Also, note that an unbalanced air-to-fuel ratio can lead to a loud bang coming from your furnace blower.
It indicates that your blower is not functioning efficiently due to a lack of complete air and gas. In this case, your blower suggests that it needs an immediate inspection and repair.
A professional repairer might detect this issue and do a thorough cleaning and necessary repairs.
In addition, we recommend cleaning and inspecting it once a year to ensure it is always safe and clean.
Faulty Heat Exchanger
In most cases, your furnace produces a rattling noise due to a faulty heat exchanger.
However, the exchanger is not necessarily faulty but has a loose panel or screw.
Fixing a loose screw doesn’t require much skill, meaning you can do it yourself.
However, ensure you turn off your furnace before adjusting the loose parts to avoid electric shock because it involves using a metallic screwdriver in most cases.
Here, you ensure you inspect your furnace thoroughly and that the access panel is well secured.
If you notice the rattling noise is not coming from a loose screw or panel, it might be an indication of a more serious problem, such as a cracked heat exchanger.
A crack or splinter may be caused by a lack of airflow due to dirty filters, coils, or blowers.
As a result, your furnace gets filled up with carbon monoxide, which may leak into your house.
To ensure the heat doesn’t damage your exchanger, ensure you inspect it regularly.
Let’s now jump to non-mechanical ways of quieting a noisy furnace blower.
Soundproofing Furnace Room
Although you might fix most of the noise coming from your furnace blower mechanically, sometimes it’s hard to eliminate its structural noise.
In such cases, ensure you soundproof its room for a significant noise reduction.
Here is how you can block the noise.
Soundproof Your Furnace
Magic erasers are good for both insulation and soundproofing.
First, it is excellent at soundproofing since it is made of melamine foam to prevent sound from going through it.
Additionally, it is excellent for insulation because it is a poor conductor of heat.
It works by curing itself into foam where its micro-structure hardens, preventing noise from reaching your living space.
Even better, they can be helpful when cleaning your furnace blower.
Here is how you use them:
- Start by making a galvanized steel sheet using wire mesh, and then sandwich your magic eraser with the sheet.
- Use the magic eraser to hold the wire mesh to the steel shit tightly.
Tightening them together avoids foam from being sacked by the blower. Note that the foam is most effective when you use it next to your furnace blower’s intake.
Here are some of the most effective magic erasers available on online today:
It is 2x thick and long-lasting
You can use it to clean different parts of your furnace blower
It is developed to clean all surfaces.
Soundproof Furnace Room Doors and Windows
Sealing your blower’s doors and window gaps can significantly reduce its noise. Here, you use soundproofing curtains or blankets readily available on Amazon.
All you need to do is hang the curtains or blankets over your blower’s door or window. T
he following are some of the quality blankets and materials you can use to soundproof your furnace’s door or windows.
- Moondream 3-in-1 sound insulation curtain-It is made entirely of polyester
- RYB Home Soundproof Blackout curtains– it comes in 3 layers, and you can easily take care of it
- NICETOWN Blackout Curtains– it is affordable and comes with an excellent material
Soundproof your Furnace Room Walls
There are two ways to do this: seal wall cracks or/and thicken the walls.
Sealing the wall cracks
This technique involves inspecting all your blower’s walls to detect any cracks, however small they might be.
Once you notice them, seal the cracks to prevent any noise from passing through.
This process requires you to use an acoustic sealant, and we recommend liquid nails since they are relatively stronger and easy to use.
More importantly, using the dampen around the wall can also avoid vibration.
Thickening your Blower’s Wall
Start by inspecting your blower’s wall.
You should thicken it to prevent noise pollution from coming into your living space if it’s thin. You can add a drywall layer to it.
Alternatively, you can sandwich the wall between adhesive vinyl sheets or green glue to make it even more effective.
Final Thought on How to Quiet a Noisy Furnace Blower
Due to temperature changes, a thud noise may also indicate an expansion and contraction of metal ducts inside your furnace blower.
However, this is a regular furnace operation and shouldn’t worry you. Above are some of the best methods on how to quiet a noisy furnace blower
Finally, ensure you regularly inspect your furnace blower according to the manufacturer’s instructions.
It helps your furnace serve you better and for a longer period.
Meet Mike O’Connor, (a DIY enthusiast), living in Cincinnati, a city ranked as the noisiest in the USA.
As a work from home dad, I have a first hand experience of how noise can truly affect your well being.
Soundproofing isn’t something that should be taken as a hobby, it should be a skill that every homeowner should be equipped with.
Most of the work documented on this blog comes from purely first hand experience, and the products recommended work as indicated.