What is your furnace for if without the blower doing its job? Is your furnace blower too loud?

The furnace blower is crucial to the function of your HVAC system, or of your gas furnace, in particular, to get sufficient hot air passing through the air ducts into each room of your home.

How to Quiet a Noisy Furnace Blower

When the blower dies, it won’t be able to send forces to the blower fan. Technically, the blower is composed of the fan and the motor. The motor and the fan are indispensable to each other, as the whole furnace blower pushes the desired temperature dictated by the thermostat.

When the furnace blower sends annoying sounds, that’s where the problem begins.

How do you silence a noisy furnace blower? Let’s see what’s happening inside your furnace system.

Why Is My Furnace So Loud?

A loud furnace indicates a serious problem in one of its components. But to fix the issue immediately, it is important to trace the source of the noise first.

Understanding what’s happening inside the furnace and the blower, it is easy to tell how things work their way and produce a loud noise. Furnace blower movement results in a loud banging or booming sound due to the interaction of gas and air.

Any discrepancy from these two elements will cause a thud since the metal ducts interact with the unsteady or unbalanced airflow blown out by the furnace blower.

Sometimes, there isn’t enough gas, or too much air will result in a wild reaction of two different gaseous elements inside. Hence, the extreme temperature collides with the metal, gas, and air, sending a loud boom to your ears.

You can only fix the issue if you know where to look.

Now, let’s get familiar with the following furnace noises:

  • Popping or banging noise
  • Humming noise
  • Rumbling
  • Screeching
  • Squeaking
  • Scraping

Below are furnace components that can cause these loud sounds.

Dirty Burner

Most likely, the booming sound may catch up with dirty furnace burners. This is when you try to turn on the burner, and there is a delay in the ignition.

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That delay, even if it were only a fraction of a second, would cause the gas to build up. And when it ignites, it will create a booming sound. The explosion happens because there isn’t an equal amount of gas and air mixture. After all, the ignition is blocked by dirt.

1. Loose Blower Wheel

The wheel allows the circulation of gas and air in the furnace. Perhaps, the metal-like scraping noise is a result of the fan hitting the blower housing. Have an expert HVAC technician check on the blower wheel before operating the furnace.

2. Loosened Blower Belt

A misaligned blower belt will cause other moving parts to generate noise. Replace a broken belt and lubricate motor shaft bearings and other metal parts to keep them from getting dry and create a squealing sound when the blower begins to power up.

3. Blower Motor

An unlubricated blower motor or fan motor will produce a screeching or rattling sound, and it is annoying and quite alarming.

Noisy Furnace Blower fan

In any case, it is dangerous to deal with electrical hazards and faults. Ask for the specific lubricant to correct furnace blower motor noise or get someone knowledgeable to fix it.

4. Fault in the Heat Exchanger

Dirt will clog a certain point in the blower panel if left unattended for a long time. The lack of proper airflow will stagnate the heat exchange and cause cracks from heat buildup.

Clean dirty blowers, coils, and filters to allow healthy heat exchange and prevent metal rattling inside.

PRO TIP: It is time to replace your furnace when it is more than 20 years old. Instead of shopping for emergency purposes, take the time to conduct routine maintenance for good conditioning unless the furnace reaches its age.


Common Noises Made by a Furnace


Rattling Noise

Rattling sound is usually caused by metal friction or metal to another material texture. The rattling noise may come from the heat exchanger being faulty and blocking the regular exchange of heat. Be overly cautious with this kind of furnace problem to avoid carbon monoxide intoxication.

Once the harmful gas leaks into your home, it can cause health problems among the people at home. Add an acoustic rubber padding beneath the furnace to dampen the sound in the blower changer and other parts like ducts, panels, and cold air return.

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Call a professional right away if you hear a loud rattling sound.

Knocking Sounds

Continuous knocking sound from your furnace blower could mean bad bearings or broken belts.

Add lubrication to the bearings and ensure that screws are correctly tightened and no loosened screw is found flying inside the panel. Once these metal parts hit something within the blower fan, they will create a knocking noise when the blower begins to move.

The loosened components will also affect the fan and the housing. It can also be due to the broken assembly of the motor.

Banging Noise

A loud bang could result from faulty heat exchange in the blower through the air ducts.

A banging noise is a gunshot sound but coming from the furnace or an explosion.

This can be fixed by checking and sealing the ducts, replacing dampers or an air filter to allow smooth airflow.

Humming and Buzzing Noise

A humming noise is normal for a furnace and an AC compressor the moment they are in operation. But a buzzing noise is different. It can mean an electrical problem, especially when you hear tiny sparks.

Avoid using the furnace and call an electrician if this is the case. Maybe there is motor capacitor failure, and it needs immediate attention.

Squealing Noise

A squealing or screeching sound is a high-pitched noise that isn’t delightful to the ears. This kind of noise coming from your furnace blower could be a broken or damaged belt, shaft bearings, and other parts that cause malfunctioning in the motor or an overheat.

Overheating will damage other parts even more if the dirt in the blower isn’t removed. Call a professional to replace the belt and let him check the overall function of the motor.

Whistling Noise

A high-pitched whistling sound means the airflow within the furnace is low.

Poor air circulation and heat exchange mean the blower has difficulty powering up the furnace to push enough heat.

Check for obstructed air ducts or vents to eliminate the whistling sound. If the sound persists, replace the air filter and have a service technician check all the vents for any blockage.

How to Reduce Furnace Noise

Furnace blower noise reduction involves the following steps:

  1. Find the weak spots before attempting to fix them.
  2. Check the ignition component. If there is a sudden burst of flame or nothing at all, something is clogging the ignition. If your furnace is a combustion air furnace-like gas, you will have to require your professional to check on that at least in a year to make sure it is continuously burning.
  3. Clean dirty filters. For thick dirt, replace it them instead of cleaning. Air cannot pass through if holes are blocked with dirt and dust. With periodic maintenance, it will not worsen the situation.
  4. Fill the gaps in the duct pipes with duct tape. The furnace flue gets worn out with the constant passing of heat and cold. Make sure that there are no gaps in the lines. Seal them properly using duct tapes or stronger ones to block harmful gases from leaking. Silicone is better for sealing the cracks.
  5. Check air duct size. If you think the noise is due to uneven or undersized duct size, replace them to improve air flow.
  6. Tighten screws and install rubber pads to dampen noise.
  7. Let a professional installer check the motor. Don’t fix it by yourself.
  8. Buy new filters if vacuuming won’t remove old dirt especially for an older furnace.

PRO TIP: Flue gases are harmful gases in the form of carbon dioxide and carbon monoxide that cannot escape the flue by ensuring that the flue pipe is not corroded. Use foil tapes to cover holes, even the tiniest ones.


11 Ways to Quiet a Noisy Furnace Blower


1. Add a Return Air Vent

To pull in back air and send it again to the HVAC system.

2. Check Oil-Canning Ductwork

This is to prevent the whistling or rumbling noise brought by the passing of excessive air.

3. Building Sound Insulation

A broad tip to work on, but you can start on the area where the blower is located. Check the layout of your furnace room.

Add insulators to reduce the noise. Insulation foam secured with a wire will dampen the noise coming from the motor.

4. Replace Loose Parts

A highly intuitive move that when something is rattling, knocking, or banging, it could be any loose parts that need replacement.

5. Fasten the Motor

Although the motor is already fastened, it can become loose in time or break the fastener.

6. Check Ignition Malfunction

Ensure that the burner ignites instantly. With many futile attempts and no fire is ignited, replace the ignition.

7. Fix the Gas Ignition

Check gas ignition if it can still be fixed. Have an expert do the repair to avoid accidents due to miscalculation.

8. Replace Dirty Filters

Clean or new filters help in smooth airflow and exchange of heat. This also prevents overheating.

9. Check Blower Fan

Bad furnace fan can mean many things: air doesn’t flow, a broken fan blade, motor failure, or unlubricated shaft bearings.

10. Adjust the Blower Speed

You can change the fan speed setting depending on the amount of air in relation to vent size and house. Set to lower or higher the fan speed appropriate for your HVAC home requirement.

11. Check the Belt and Oil the Motor

A Misaligned or broken belt will hamper the function of the furnace motor and fix it in place. Add lubricant oil to the motor for smooth operation. Old and cranky motors will cause overheating as their parts will struggle to work. Buy the right size of belt your motor need.

PRO TIP: You can sense that your furnace is dying when you get headaches, nausea, burning nose, and eyes. This means that the air flowing inside is a harmful gas instead of the ambient air your furnace is supposed to blow.

What routine maintenance helps reduce furnace blower noise?

A: The best and easiest routine maintenance you can do to reduce the furnace blower noise is adding oil or lubricant to corrosive parts and cleaning and replacing the furnace filter if needed.

How much does it cost to fix a furnace blower?

A: You can spend around $150 to $2000, low to high, respectively, when replacing an old and worn-out blower motor

How long does it take to replace a furnace blower motor?

A: Whether with the help of a pro or DIY, it will take between 45 minutes to 90 minutes to replace the furnace blower motor. But this also includes cleaning the fan and filter, adjusting the belt, testing, and putting everything back together.

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How do you know when your furnace needs to be replaced?

A: The signs that you need to replace the furnace are:

  • Frequent repair
  • Increased humidity/thermostat not working
  • Old HVAC system
  • Corroded parts, hard to remove dirt
  • Rising energy bills

PRO TIP: An air source heat pump can be used along with a furnace to improve your home’s heating system.

Conclusion

A noisy furnace blower is a pain in the head if you have no idea what to do.

In summary, no matter how huge your house is and the complexity of your HVAC build, the noise will always depend on the faulty component. But if you have a fair understanding of your HVAC engineering, it is easy to point out which part is causing what noise.

The ultimate goal for mending these broken parts is to get rid of the different noises you hear. And the excellent take is that the furnace gets proper maintenance to provide ambient air and save you more on energy bills.

So before everything becomes too late, have your furnace blower or your entire HVAC system handled by a professional HVAC technician to fix and prevent any problem from getting worse.

You can now sleep peacefully or go about your day knowing that everything in your heating system is appropriately attended to and that a healthy air flow fills your home.

Robert Castelao

Robert is an electronic engineer with more than five years of experience with a solid affinity for helping people reduce noise. He writes about these silent home appliances and easy soundproofing measures to help everyone avoid the negative effect of extended exposure to high noise levels.

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