Dan has been in the HVAC industry for 23 years with experience ranging from installation and service to sales and distribution.
Does your furnace remind you every time it's running by offering you a "bang" or a "squeaky, squeaky, squeaky" noise? Sure, we are glad the furnace is on, but who wants the life scared out of them or to have to turn the volume up on the TV to mega-loud?
More often than not, noises from a furnace and duct work are simple to fix and can be remedied rather easily with household items or small purchases from the local home improvement store. Let's take a look at some of the noises a furnace makes, where exactly they come from, and how to fix them.
Scary Furnace Noises
Does Your Furnace Bang Every Time It Comes On?
The wonderful "wha-boom" noise you're hearing when your furnace comes on is likely one of two things. It could be your duct work doing what’s called “oil-canning"—that is, flexing when the pressure changes—or, less likely but more serious, it could be a small explosion called a “roll-out.”
Possible cause 1: Oil-canning duct work. Go to the furnace and listen carefully at different places to see if the banging is coming from some place in the duct. If your duct is oil-canning, it likely has a weak spot and needs support.
You can easily fix this oil-canning by screwing a slightly thicker piece of metal across and onto the spot. Though it may sound silly, you could even whack that spot with something to dent it in, though I don't recommend this being your first choice.
Possible cause 2: Ignition malfunction (roll-out). This is not very common but can be scary—a little explosion when the furnace starts up, or a burst of flame bigger than it needs to be. To see if banging is caused by a gas ignition problem, watch the furnace start up. Leave the doors on the furnace so that you aren't affecting the observation.
If you can see into the furnace doors, you should be able to see what is happening. If not, listen to pinpoint where the noise is coming from. Watch to see if the doors on the furnace shake at all. If so, then try again with the door to the burner compartment open to see if the banging still happens and if you can see what happens when it does.
If you see extra flame or shaking associated with your noise, the good news is that you've identified a potentially dangerous problem in your home and can now correct it. The bad news is that you will most likely need help correcting the problem; messing with the gas portion of your furnace is not recommended. You may feel better to know that newer furnaces have a “roll-out sensor” that will shut down the unit if this problem occurs.
Is Your Furnace Whistling?
If your furnace is whistling, ask yourself, "Did this just start, or has it always whistled?" This will help determine what you should look for first.
Possible cause 1: Dirty filter. Especially if this whistling has started recently, check your filter. It may be clogged and causing the fan to suck air from anywhere it can. Even tiny holes or spaces will whistle if any significant air is being sucked through them. To test this theory, pull the filter out and see if the whistling stops.
If your filter is so caked with dirt that it is clogged and stopping the flow of air, you are better off just taking the filter out (while you arrange to go get a new one). This is better not just for the noise but also for the wear and tear on your fan motor.
Possible cause 2: Gaps in the duct. Try to hear where exactly the whistle is coming from. It will likely be a small hole near where the duct connects with the furnace close to the blower.
To resolve this problem, tape up the gaps with a quality HVAC foil tape. Duct tape or clear hi-temperature silicone can be used in a pinch to seal them off. Foil tape tends to work very well, and if you take some extra time to seal the various junctions in your ductwork while you're there, it'll even help make your system more efficient. I suggest you use a foil tape like this one by Impressa Products. Foil tape can take the heat in your ducts a lot better than standard duct tape can.
Possible cause 3: Ducts too small. If the whistling stops as soon as you take the doors off the furnace, it may have gone away just because you've opened up the unit and relieved the suction that was being created. If you can’t find any another cause for the noise, it could be a sign that your ducts are improperly sized; your furnace wants a greater flow of air.
Do You Have Rattling in Your Furnace and Ducts?
Vibrations and rattling are simple fixes usually. Here are a few things you can do to stop these annoying sounds.
- Add more screws to loose ducts.
- Duct-tape loose pieces.
- Add rubber or cork pads under the unit where it sits on concrete or blocks. (Yes, you can likely raise the unit with a pry bar just enough to slip something thin in there.)
Do Your Ducts Bang or Squeak When You Walk on the Floor?
Possible cause: Duct work not secured right. The duct may be too tightly secured to the ceiling below you, or the metal panning may not have been nailed up correctly. Either reinforce the duct as with an oil-canning duct, rehang it, or replace it with "Thermo-Pan.”
Do You Hear Whooshing?
Possible cause: Not enough air coming through. Is the air passing through the registers (the screens that let hot air into and out of your rooms) just plain loud?
You may need some duct resizing or additional return air added to your system. This will quiet things down. Temporarily, use a cheaper filter—a more permeable filter, with more and bigger holes—and change it often to keep it clean. This will allow more air to pass through the blower.
Do You Hear Motor Noise?
Possible cause: Old motor bouncing, or wearing out its bearings. Walk around and listen to see whether the sound is coming from a motor. Try to describe the sound it’s making; this can be useful to anyone who may assist you.
In some cases, an old unit may be weak and allow the motor to sort of bounce as it runs. You may be able to place a sturdy piece of styrofoam under the squirrel cage to stop this, but if the bearings themselves are the culprit, you may need to call a professional.
There Are Many Noises a Furnace Makes and Different Reasons for Them
These tips cover most of the furnace and duct work noises I'd been called out on in my 22 years of HVAC field experience. Though most of these problems are simple to repair, the charge for HVAC service is the same whether the problem is simple or not. That’s why I try to point it out here when there is a problem you may be able to fix yourself.
Some noises aren't easily fixed. They may require professional help, depending on your mechanical abilities and knowledge. But your observations could help a professional fix them.
I invite you to describe your own issues with HVAC noises—from the furnace, A/C, exhaust fans in your bathroom, and so on—in the comments below. I will do my best to offer some advice on things that you may check and the simplest ways I know for you to fix them. We all need peace and quiet sometimes, and the last thing we need is our house yelling at us during those times.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: When the doors of the furnace are on, the furnace 'buzzes' very loudly like a large bee stuck inside. If I take the doors off, or only partly put them in place, it is quiet. Is it having difficulty drawing air?
Answer: I would say there is a very good chance of that. Make sure the filter is clean. Upsizing the return duct or adding returns can help. Using a cheaper filter can help but has it's an obvious trade-off.
Question: Our furnace venting motor is noisy. I was told that it would be $1500 to replace but that as long as it continues to work there is no need to replace it unless the noise is bothersome. Can this be repaired or is the replacement the only solution?
Answer: $1500 is an insane amount of money for an inducer motor. These aren’t hard to replace even if a kit repair is needed. The most expensive motors and motor kits are around $600-800 in the highest end of furnaces and $700-900 in labor is robbery. An average furnace inducer motor assembly is around $200-300 and takes maybe 2 hours to replace. Please get a second opinion.
Question: My furnace makes chirping sounds about 2 1/2 minutes into the furnace cycle up. I have already replaced the blower venting motor, the inducer housing assembly, the Flame sensor, and igniter. There are new batteries in my thermostat. I still get the chirping sound then the furnace cuts off. I have a new filter installed as well. It's driving us nuts. What could it be?
Answer: It’s possible the issue is the blower motor or better yet the wheel itself. If it’s out of balance or the shaft is wobbling that could be the problem. Perhaps it’s a combination of all those things, and a blower assembly may be needed. I can never guarantee an online diagnosis, but this is what I would be looking at.
Question: We just had a new HVAC unit installed. I was not sure if the old unit was a 3 1/2 ton or 4 ton, so we went with a 4 ton. Now the return air fan, which happens to be just across from the bedroom, is so loud we cannot sleep at night. It does pull more air through it than the old unit did. Is there anything we can do to quieten it down?
Answer: Well, you may ask them if they can slow the fan, but it has to carry a certain amount of air for the A/C to work. Since you opted to go with 4 tons, you needed more air. Your contractor should be the one telling you what size you need based on math. Not a guess. Rule of thumb is to go smaller with an A/C if it’s close, not bigger. Bigger is also likely to “short cycle” where a smaller unit that runs more but starts and stops less often is actually more efficient and does a better job of dehumidifying which is what an A/C really is, a big dehumidifier.
Question: Our furnace (heat and AC) blows very loudly, and this was not always the case. It also wasn't a gradual change, but a sudden one. The furnace is a Payne, and just tonight I learned there is a second filter inside of the unit, which hasn't been cleaned or changed seven years. We always just changed the filter on the exterior of the unit. Could the interior filter be the issue?
Answer: Yes, it is very possible and if it’s been that long it may have taken a toll on the motor. I would change and clean that filter.
Question: My AC/furnace started making noise a few days ago. It has progressively gotten louder and louder. It definitely sounds like the motor or even the fan blades are clanking. When I stand outside the unit, it is definitely where the noise is coming from. The blower motor is still working, but it does not seem like it is blowing as hard as it should. Will a simple cleaning of the motor and replacement of the filter fix the problem?
Answer: I’m not sure what the clanking is, but if the outdoor unit is malfunctioning it could cause the indoor coil to freeze and restrict air flow. While I never turn down good maintenance practices, I don’t think that is your problem.
Question: Air rushing in my furnace and making a loud noise. Is this normal?
Answer: It’s not necessarily normal but it’s common. Often the return duct size needs increased.
Question: My furnace fan makes so much noise. Would replacing its filter help with noise reduction?
Answer: Replacing your furnace's filter fan can definitely help if the filter is dirty. It's like a vacuum when it's set to "low" or when a fan tries to suck air through a dirty filter--you hear the noise difference. The difference can be more or less noticeable depending on how dirty the filter is and if the return duct is sized correctly.
Question: When the furnace is on there is a loud low rumble coming from the vents on the other side of the house. Sounds like a train in the distance. So annoying! How can we muffle that?
Answer: First, you have to determine the source of the noise. Is it mechanical? Or is it air movement? Or is it the flames? Then perhaps it could be determined why it's only at one end of the house. Is it because that's a bedroom and it's quiet when you're in there? Is it why you only notice it there? This is what I would be checking to start.
Question: What causes the furnace to sound like thunder?
Answer: Perhaps oil canning in the duct. Some higher powered furnace flames can resemble a jet sound.
Question: What causes the gas furnace to sound like a door shutting when turning on? After that, it works fine!
Answer: It's likely just the pressure change in the unit/duct pulling loose items tight as the fan creates a vacuum.
Question: Will I have an explosion if my furnace is causing my house to vibrate?
Answer: Not likely, but if it's that bad you should call someone out. It's probably blower related.
Question: Why does my automatic vents that open and close to heat zones make noise when the vents are moving (an annoying sound) as they turn. It echoes up the ductwork and scares my young kids. How can I fix that? I tried spraying WD-40 on the exposed parts.
Answer: If you've oiled them then perhaps they are just getting too old or scraping against some other parts of the duct.
Question: What causes a furnace to bang or pop when it's running? This happens often after it stops heating and is in the cool down process.
Answer: The expansion and contraction of metal during the heat up and coil down is the typical cause of these types of noise.
Question: What causes the furnace's blower motor to fluctuate in speed ?
Answer: Different modes (a/c, heat, fan) will sometimes run at different speeds while some furnaces also have features like 2 stage heating or cooling which will change fan speeds as well as variable speed and modulating units.
Question: I just had the capacitor in my furnace changed, but it is now making a whistling noise that it did not make before the repair. What is wrong with my furnace?
Answer: It's possible the unit is running better therefore perhaps revealing small holes in your ducting. If these gaps were plugged with dust, you wouldn't hear it or perhaps the blower was working too hard thus not moving as much air so now that it is, it's revealed that you have leaky ductwork. Pinpointing the whistle and simply putting a piece of tape over it should fix the issue. That's my guess from here.
Question: I hear a whining noise at the end of the furnace's heating cycle. Would this be a light oil or belt replacement?
Answer: Neither would hurt. Perhaps check amp draw on the motor. If it's high it might be on the fritz.
© 2012 Dan Reed
Connie on January 18, 2020:
I live in a mobile home, and the furnace is located right next to the living room, in a closet, making it difficult to hear the tv when it’s running. Is there anyway to reduce the noise
Carol Reid on November 08, 2019:
I have a brand new Bryant gas furnace. It is louder than my old furnace. I thought a newer one would be quieter. My is it so loud ?
debby on April 02, 2019:
I have a 5 year old gas furnace. About 30 seconds before the end of a heating cycle, it begins to rattle and stops when cycle is over. No odors or no heating problems. When it was serviced, I was told it could be a problem with the heat exchanger and it would cost several hours of labor just to get to the heat exchanger to check. Is this right?
Harry on March 24, 2019:
I have a downflow furnace underneath the filter the sheet metal is loose I can press on it the raddel noise goes away how can I fix this
Brittany on February 18, 2019:
My furnace is making noise from where the motor is after a few minutes of being on than I start smelling something burning.
Tom on January 03, 2019:
I am hearing a knocking noise once while the heater is running in the middle of cycle and once when the heater is also not blowing air what could this be?
Dan Reed (author) on October 16, 2018:
Perhaps but in a new system...I wouldn't be happy with that answer.
JUDITH WISE on October 12, 2018:
we just got a new williams furance and when it turns on it makes a loud banging noise...service came out and said it was going from cold to hot..proably combustion????is this true
Dan Reed (author) on June 17, 2018:
There are a lot of things that can impact sound. Did you try my suggestions in the article?
Surrinder on June 17, 2018:
My Lennox its only 3 years old and sounds like an aeroplane taking off. Is there any way to quieten it
Dan Reed (author) on November 02, 2017:
Shirley - If the unit is 2 weeks old you need to call whoever installed it and have them make the repair. It's under warranty and their labor should be covered on a brand new install if there is an issue.
Dan Reed (author) on July 21, 2017:
Well, though I can't say for sure if they were correct or not. It's possible the motor installed is simply different and thus may notice difference since you've been accustomed to hearing it a certain way for 30 years. Another would be that it's a cheaper motor that function is more important than decibal. There are higher end motors that have lower DB ratings....you could perhaps ask to have a better, quieter motor installed. Thanks for reading.
Rhonda Buffkin on July 21, 2017:
I had a company come out and replace the fan motor because the ac was freezing up. It now has a hum. Called them back. They said because it worked,it was fine. I have live here 30 years and never had this problem with 2 units. Should I press the issue, is something wrong.
Dan Reed (author) on June 01, 2017:
There are very quiet furnaces on the market. They are not the cheapest however a variable speed motor can help a lot. Not sure if you're getting a loud fan noise or firing noise or both but newer high efficiency furnaces offer a lot less noise. Thanks for reading.
Yvonne Tarango on June 01, 2017:
We purchased the house new but when the furnace turns on its loud and it stays loud till the it turns off. Are there quieter furnace ? Guest just turn around startled when the heater or AC turns on! And about raising the volume on the TV while it's on is correct! I want a quieter FURNACE if there is one!
Dan Reed (author) on February 27, 2017:
Susan - That could be so many things. Perhaps something got shook loose during install that's now ticking that didn't before. Could be that the new motor is working so much better than the old that it's revealing other issues??? Sorry I can't help much with that. Try and locate the clicking and that should help narrow down the possibilities. Thanks for reading.
Susan on February 27, 2017:
We had a house built in 1971, we just change the furnace motor cause it's making a noise and works well , now we hear noise once in a while that's kind like clicking and annoying any help .
Darla Atchley on January 17, 2017:
We have a new one story home less than a year old. The HVAC system is in the attic space that is over one corner of our master bedroom. I can hear the mortor start up, ignite and run and shut down. I have called the builder out and HVAC company 3 times this past year and they say nothing can be done. Also the return air in the hallway is very loud and can be heard in a lot of areas of our home. It is a Carrier system. Are there sound absorbing materials to help with the furnace noises and what can be done about the return air noise? This noise is waking me up at night. Not sure what to do next. We are still under warranty. I personally feel they put it there for their convenience. Thanks
Dan Reed (author) on January 06, 2017:
Lidia - A dirty filter will make a blower loud and that can be done for just a couple dollars so do that for sure. If you don't, you may end up needing a new motor regardless. If it's still making the noise, you still should have a pro come. There is too much for me to guess at and if you're not confident about doing it, you probably shouldn't. If times are real tough, many localities have emergency heating services they can provide. Thank you for reading.
Lidia on January 05, 2017:
I live in a house that is about 17 yrs old, has original gas furnace. Lately I notice that it is getting loud, kind like an engine when you are going to fast for second gear. We had it checked last year, but we have not changed the filters this year. Could a dirty filter make the motor run faster? Thanks I do not know much about furnaces and do not have the money to have a professional come to check it they charge Ninety dollars just to come to the house. Thanks Lidia
Dan Reed (author) on December 04, 2016:
Gene - Yes. That's not a fault of the manufacturer. The contractor should be familiar with this on Carrier and perhaps he was and it was just an oversight. It happens. It's inconvenient but he is human. Glad it was easy fix.
Kate - Yes, and ECM blower is very quiet. That said, 70K BTU seems like you must have a good sized condo?? I heat around 1800 square ft with an 80K BTU unit and could probably go a bit more with that. And with you having likely less exterior wall space...just spit balling but that unit seems big for the typical condo in my area which would lead to loud airflow perhaps since bigger BTU units have bigger blowers usually. Something to consider?
Thank you for reading.
Gene maccarano on December 02, 2016:
Anyone having an issue with their Lennox slp98v furnace with resonance sounding throughout the ducts. My problem was the contractor didn't remove the shipping bolt on the blower. Hope this helps someone.
Kate on December 02, 2016:
I had a new Carrier Comfort 80 single stage furnace installed in a 30 Y/O condo rated at 70K BTUs. Its is so noisy that I called the installation company back. Short story - nothing is wrong with it but the noise is intolerable in a small condo. They are recommending an ECM motor and raising the unit up off the floor with a riser box to quiet its function - for another major cost on top of what I have already doled out. Will these steps quiet the furnace? Also, will an ECM motor run quietly in AC mode as well?
Dan Reed (author) on November 12, 2016:
Joe - It sounds like the inducer motor is going to go, or the wheel is out of balance, or something is stuck in there...maybe even a bird. At any rate, any interference with that will cause it not to pull in the pressure switch and is likely why the unit kicks off and then maybe next time it gets a little better suction so works for a bit but then again, rinse and repeat. I would take a look in there to see if anything is blocking it and if not, it may be time to replace that inducer unit.
Thanks for reading.
joe on November 12, 2016:
i have an airflo. the induction motor is getting noisey. the furnace will cycle ok however it shuts down and will not ignite until i flip the main switch. then it will work for a while
Dan Reed (author) on March 14, 2015:
If it's when it shuts off and it's aged, it could just be more sensitive to the drastic temperature change and something is "oil canning" on you. I can't really think of anything else it could be so long as no fire or gas is involved.
Wayne B. on March 08, 2015:
My gas old boiler now makes a couple of popping/ boom sounds when it shuts off. I cleaned burners & still does it. Any suggestions?
Dan Reed (author) on February 05, 2015:
Anthony - Thanks for the reply and good luck.
Anthony on February 04, 2015:
Thank you,Cre8tor, I happen to be an auto mechanic, I appreciate your feedback I did try without a filter already, I have great suction from the return and blows excellent into the rooms, I did notice today on the sides of the blower at the bottom of the furnace the ducks seem to be sucking in on the sides, maybe it always did that I'm not sure, there really isn't much to it, furnace's are very forgiving compared to cars, this one's got me stumped, the cage and the bearings are in excellent condition, no movement in the bearings at all,What I think I am going to do is let it go until it's something very obvious, I only hear it when I'm in the garage anyway But thank you very much
Dan Reed (author) on February 04, 2015:
It sounds to me like there's not enough air coming back to the unit and perhaps it's trying to suck air through small gaps that are whistling/squeaking or that a door/panel is being sucked up against another metal surface. Either way, it could be a clogged filter (which with all else you've done I'm sure you've checked), need more return air vents or larger duct coming down to the unit. If you're using a good filter, you're also cutting airflow so maybe try taking out the filter and see if the noise changes...if it does, it's likely a good hint to the lack of airflow coming back to the unit. Hope this helps and thanks for reading.
Anthony on February 04, 2015:
Hi,I have a noise in the blower area only when the door is on, I took it all part and nothing is rubbing it seems only when there's pressure with the door closed it makes a squeaking noise, I thought it might be the motor so I bought a brand new one,it sounded the same, so I changed the fan belt that was cracked still have the same noise, the cage and the bearings are perfect spends without a noise when I remove it from The furnace ,Definitely not clogged I got under the furnace with A mirror,With the furnace running if i move the furnace slightly the noise changes a little bit, thank you..Any ideas would be grateful
Dan Reed (author) on December 24, 2014:
Len Sciarra - This is. Especially if you only have about 10' of pipe between the furnace and where it's poking out of the house. DO NOT be temped to put anything over that pipe to kill the noise or keep critters out. It will shut down the furnace especially once it's cold enough to freeze the condensation that comes from that pipe. (See my comment to Bill)
Dan Reed (author) on December 24, 2014:
Bill - This is likely your inducer fan. (the fan that blows air up the chimney/flue) Brand new, these tend to run so well they will create a whistle through the tiniest of holes. Check to see if this is where it's originating from and if there are any tiny holes that you might be able to seal. As the unit heats up, it will tend to quiet the noise and in time, often it will dissipate or correct itself. Also check to see that all the piping tied into that fan's housing is sealed and well connected. That said, this is not all that uncommon. Particularly if you had an older unit without an inducer fan. Now that you have one, you'll notice it and it will stick out sorely to you since it's a new sound. Hope this helps.
Dan Reed (author) on December 24, 2014:
Kevin - Perhaps check your dampers. You may have them closed. Whichever way the handle is pointing is the way the damper is turned. You want the handle pointing in the same direction the pipe is going to be open. Otherwise, check for any obstructions in the pipe or the register itself.
Len Sciarra on December 22, 2014:
We have a moderately new furnace and on the outside, (maybe ten feet of PVC pipe) where the fresh (combustion) air intake is, it makes a ton of noise. Is this normal? Thanks
Bill on December 22, 2014:
We just had a Lennox furnace installed by reputable service people, and now there is a noise like a ships whistle blowing just before it leaves port for about 7 to 10 seconds before the furnace fan starts to blow hot air. Does not happen every time, but it is annoying as you can hear it all through the house, and you know 10 seconds later, the fan will start to blow. Can't seem to get any help with this.
Kevin on December 21, 2014:
Just moving to a new house, There is two air blowers in the master bedroom under each window, but only one make a lots noise. the noise come every times when hot air out, just like very strong wind blow out. The same thing with another room, but the third one does not have the problem
Dan Reed (author) on November 13, 2014:
Gene - Installing a flexible duct connector is usually an option so long as there's room so it's not pinched. Speaking quite frankly, you won't get much help with this as motor sounds, electrical buzzes, ticks and air noise are very subjective and though you may not be happy with your system, it may have tested better than many others. Certainly laying right above the system in the still of the night, your going to hear a motor run or perhaps vibrate or the sound of 2000 CFM rushing into the plenum and then slowing and unfortunately, it's the nature of the beast. Another sad truth is simply that most homeowners don't sleep that close to their unit so during the hustle and bustle of the day, they hear nothing and when 2 stories above or on the other side of the home...still nothing thus making you seemingly the only one complaining. Perhaps this is a bit of cold water but I'm not trying to be snide, just factual. I have to think if there was a simpler answer, the contractor would've resolved the issue. I never would've left a customer unhappy if there was an easy way to fix their issue. I'm thinking that you may want to consider have your plenum and first few feet of duct lined and resized. The liner will certainly help and resizing the return can slow the air as it enters the fan...you flexible connector could help too. I warn you though, this will not be cheap and in defense of your contractor, isn't really standard service with a furnace replacement unless there was a conversation about such and then no follow through.
gene maccarano on November 12, 2014:
The noise we hear has been there since the unit has been installed. The contractor who installed it had been contacted and they said that it was a normal noise for a variable speed motor and that changing the motor would maybe solve the problem but said that there would be a slim chance it would correct it. I also asked if there was a brake system that maybe could be reprogrammed that would ramp it down differently or even let it freewheel, they said no. I also was wondering that if it was possible to install a flexible duct connector between the furnace and the supply duct to maybe cut down on the noise. They said they would do this for a cost. There is one installed on the return line, but none on the supply. I'm running out of options and my contractor doesn't seem the least bit concerned about helping me solve this. I called Lennox too and they weren't any help also.
Dan Reed (author) on November 12, 2014:
If you've recently purchased this unit, certainly you should have that company come and diagnose this before long and repair the issue. Is this a new noise or has it been this way since installed? Some fans do cycle off and on between speeds and/or functions so the RPM constantly changing would be normal as would air pressure changes. Perhaps the sound is more a result of the duct sizing than the unit itself. Too often duct sizing is overlooked and people are unhappy with certain aspects of their new systems. Depending on the age of a home, new equipment can have major draw backs because the old duct system isn't scaled for today's equipment and is far more sensitive.
gene maccarano on November 11, 2014:
We purchased an SLP98V Lennox gas furnace. We are noticing a a resonance that echoes throughout the ductwork when the variable speed motor hits certain rpms of the motor ramping down. I've insulated the ceiling but unfortunately that didn't help. We have a bedroom above the furnace room and the furnace starts and shuts down every 10 minutes. The noise is very annoying. Is this a normal operation of this motor. I would think it would be more quiet like everyone has bragged this furnace to be. Do you have any suggestions? Thanks.
Dan Reed (author) on November 11, 2014:
Joel - You're fine to hold the button. Just don't stick your hand in there. Observe only. Try to pinpoint the source.
Joel on November 09, 2014:
Our Goodman Furnace squeaks when it is running. Any ideas? Should I take off the panel and see what is squeaking. I know there is a shutoff when the panel is off so I would have to keep my finger on the shutoff, but I don't know if that is safe to do?
Dan Reed (author) on November 06, 2014:
A cleaning is a good idea. The burners shouldn't be building up too much dirt or debris...if it sooting badly, that's not good and means you're not burning fuel at the proper rate. At the beginning of a season, your exchanger will be expanding more than it has since last year and then sort of level off after a couple cycles so some cracking and popping at a reasonable level isn't abnormal but if it's continuous and sooting, you may have a problem that really should be looked at. Keeping in mind, I only have my imagination to
Popcycler on November 04, 2014:
Wow .. thanks for the prompt response.
1. The unit does not shut off prematurely ... it completes its normal cycle.
2. I'm 99% sure the noise isn't coming from either motor.
3. The vibration (?) rattle appears to come from the burners (4 of them) area or in back of them.
4. The noise has diminished in the last 2 days and is no longer continuous but spotty and quieter.
5. The burners are dirty ... and the furnace hasn't been professionally cleaned or serviced for some time. Maybe that's what it needs?
Dan Reed (author) on November 03, 2014:
Popcycler - It would help to know more about what portion of the furnace the noise is coming from however it kind of sounds like there may be something stuck in the inducer motor or the blower motor. If either are not getting the proper air flow, it's possible it would allow the furnace to start but once the readings aren't where they're supposed to be, will shut down the unit for safety precautions. I would take the doors off the unit, push the door button with my finger and see if I couldn't more specifically point out the noise or see something that's obviously not where it should be. Thanks for reading.
Popcycler on November 01, 2014:
Bryant Plus 80 variable speed gas furnace starts to rattle (sort of loud, random ticking sound that is only audible right by the furnace) about 45 seconds after the burners ignite ... and stops immediately when the burners shut off. Suggestions? Thanks
Dan Reed (author) on October 09, 2014:
If it's that big of a boom, you need a technician. Otherwise, check the duct work for oil canning.
Dan Reed (author) on May 02, 2014:
Hi Faith. You need to take the doors off the unit and see if you can pinpoint the noise. It could be something in the firing and that would need immediate attention. I wish I could offer more at this time but this isn't one of those, "Oh, yea. It's this...." type of scenarios. If you can't pinpoint it yourself then I suggest calling in a technician because it's not something I would let ride.
Faith on May 01, 2014:
My furnace just started making some new sounds. It starts with a humming sound. It took me a couple nights to figure out that the noise was coming from my furnace because the heat wasn't coming on. Once I figured out it was my furnace, I cranked my heat up to see if the furnace would actually kick on. It did, but was making a clicking sound for at least a minute before it actually started. I was getting warm air out my vents, so I turned the heat back down. The furnace shur back off, but for the last 15 minutes since, it has had a banging sound. At first it was every few seconds, and it has slowly been decreasing in frequency so that it is now every minute or two that it bangs. Any ideas as to what could be going on?
Jay desai on March 20, 2014:
My furnace is under my family room in basement. My return duct is in my family room in one corner. When the motor run for heat or air condition I hear a loud noise through my return duct in family room which is disturbing in my family room. Should I add insulation in my return duct and also over rap the duct from outside in basement . My email is firstname.lastname@example.org . Please advise my expense for inside duct insulation is about $500. Do you think this is the right price for insulation.
Dan Reed (author) on February 03, 2014:
@peter - Well, if it's not working at all, it's probably the capacitor but a capacitor works or don't so if it's intermittent, then I would say your motor is on the fritz. A motor making a brrr sound is usually due to lack of power (especially on start up...thus what the capacitor is for) or locked rotor. Locked rotor or bad start up can trigger little sensors on the housing to shut the unit down due to overheating (which the motor has a heat limit too) or as a safety because it knows the fan isn't running so can't let the heat run or dangerous issues can occur.
Hope this helped and thanks for reading and commenting. Share with your friends!
peter on February 03, 2014:
my furnace blower sometimes works and sometimes it just starts with a brrrrr sound and then stops . secs later starts again brrr then stops .i have changed the belt still same thing .what could be the problem .thanks
Dan Reed (author) on January 27, 2014:
@llcmunch - Most likely, it's the contracting heat exchanger. As it cools, the exchanger and other parts of the cabinet contract and can make a clicking/ticking type of noise. If it's clicking in the inducer housing that was just worked on during operation, that's a different story and perhaps a screw got dropped or somethings rubbing but if it's just in cool down, probably not to worry.
Thanks for reading and if needed, there are other of my hubs that might answer more questions about furnace operation and such.
llcmunch on January 27, 2014:
Just replaced the Furance Inducer Blower motor now during the cool down cycle there a clicking noise that has stared up, what could be the cause of that.
Dan Reed (author) on January 25, 2014:
@hen - There is a lot to be said about your comment. I don't usually do this but here are a couple of links to other articles that might help. These should help at least narrow it down and perhaps then I can help some more.
To help pinpoint problems:
Help to clean your coil and products to use:
hen on January 25, 2014:
My furnace always cycles off and on.Filter is clean, I do have central ac.Could it be the coils or fins are dusty? How could I clean it from the inside?Will I have to cut a hole to get to it?
JCarter4 on January 24, 2014:
Thanks Cre8tor, I'll someone check that out. Thanks for the suggestion.
Dan Reed (author) on January 23, 2014:
@JCarter4 - Interesting. My first thought would be filter too but...if you have air conditioning, it's possible that the evaporator coil is dirty. (One thing people don't think much of with all the emphasis on filters.) Though you may not be using it now, air still flows through the coil and if it's dirty that could be a likely culprit. Seeing as how cold it's been in the US, our furnaces are running a lot and therefore more dust is being disturbed and drawn in so things get dirty quicker. The dirtier they get, the faster they get dirty. Sound silly? Well consider that the more the coil or filter is clogged, those tiny particles that got through before can't now. Hope this helps. There are some other possibilities but this is most likely.
JCarter4 on January 23, 2014:
The air returns for our HVAC system are suddenly much louder than they used to be... the air moving through the vents is loud. At first we thought it must be dirty filters, so we changed them... they didn't really look very dirty. That didn't fix the problem. Why would they suddenly be so loud... could cold outdoor temps have anything to do with it, do we have a fan issues... we're stumped. The house/system is 5 years old.
Dan Reed (author) on January 19, 2014:
mwesby - No. Certainly you are not alone, thank goodness or I would be out of work all together.
Whistling is very rarely a danger type problem. Annoying yes, danger, not typically. See, whistling is one of the most inconsistent issues because it can come and go based on temperatures, pressures, cleanliness or lack of...again, I suggest doing the best you can to locate where it's coming from to try to remedy the problem or determine if there is any danger. With a 3 year old furnace, I would guess it's the duct whistling, not the unit itself.
Thank you for stopping in!
mwesby on January 19, 2014:
My first reaction to everyone's furnace issue was humorous. I am thinking boy i am not alone with the furnace whistling, tapping, and the loud noises when it ignites. After 3 days the whistling has stopped. Since we were not here 4 days prior not certain how long it was whistling. After reading wayseekers comment however i am now wondering even though the whistling stopped should we still be concerned? Any thoughts? Furnace 3 yrs old. House built in the 1950s.
Dan Reed (author) on January 10, 2014:
Actually, it's not surprising and sounds as if he did good. The oil may be from oiling of the motor since otherwise a gas furnace doesn't employ oil. If it worked, and the motor/fan is working better, it may have exposed leaks in your ductwork. With the fan working better and the air moving faster through a new filter as well, small gaps in ducts tend to whistle. You can by duct seal, mastic or foil tape to seal these. Try to find the source of the whistle. I do my best online, but this would be my first guess. Thanks for stopping by. I have multiple furnace Hubs that may answer more questions.
matt on January 10, 2014:
I just had my furnace serviced. Now it has a whistling noise and there is small amout of oil leak near the furnance. It never whistled or leaked until it was serviced. What's going on? Thx!
Brandon Hart from Atlanta, Georgia, USA on January 09, 2014:
I have an older furnace, so I think that it's a little bit louder than it should be. I'll be using some of these tips. Thanks again.
Dan Reed (author) on December 27, 2013:
@PatF - An ECM blower is to be pretty quiet so something is amiss if it's that loud. The blower can be adjusted down in some cases and might help but usually is factory set to recommended speed for unit size. This is the easiest and first thing I would ask. Next, many times when a new unit is installed to old ductwork, the old ducting isn't sized right for it. (Not much thought went into old duct sizing) Adding a bigger "collector box" might help. (Last piece of return air duct where the air drops from ceiling toward filter/furnace) That said, resizing ALL the duct is often expensive and impractical. Lastly, the unit could be too big for the home. I assume it's not (shouldn't be) but is possible. This would be very difficult for me to confirm online. (Adding supplies and returns throughout the home will also relieve some of the pressure thus noise as well. Just don't add return air to any unfinished areas, kitchens or baths) hope this helps and thanks for reading.
PatF on December 27, 2013:
We have a brand new Carrier high efficiency gas boiler system (Bosch boiler) with infloor heating in the basement but force air ducting on main floor (bunglow). It's a fairly open concept home with basement unfinished, but the loudness of the furnace when its running and the sound of the air moving through the ducts is very loud and for the money we paid for this system I'm just not happy with it. I believe its supposed to have an ECM motor, but there's nothing quiet about this system. Is there something we can do or check to fix this? Our installer doesn't seem to think this is an issue. Any help you can provide would be greatly appreciated!!
Dan Reed (author) on December 27, 2013:
@boots4real - you definitely need to get a tech back out there from the sounds of it. Gas build up is a serious problem. If you have a pilot light, it should always be on. I can't say what the cause of your problem is for certain but wouldn't mess around with it. Thanks for reading and would be interested to hear the diagnosis.
boots4real on December 27, 2013:
My furnace makes a big boom when it cuts on.I had a new thermocup and box put on and its still doing it just not as much.I watched it to see where the boom was coming from and it was from the gas coming out then it lights.but now the pilot light seems to never go out.its a pretty BIG BOIM ITS STARTING TO SCARE ME.
Dan Reed (author) on December 17, 2013:
Hi Lynn. It's likely 1 of 2 things. Let's hope it's just oil canning. The fan pushes the air pressure up in the duct. When it's shuts off, the pressure drops and the duct will bang (oil can) as that happens. Try to pinpoint and secure that spot as instructed above.
You have to find out where the "backfire" noise is coming from. If it's in the burner assembly area, I would call a service tech out soon to have it diagnosed. This could be dangerous or just get worse if not addressed.
Thanks for stopping by. I have multiple Hubs on hvac that perhaps can help in the future.
lynn on December 17, 2013:
My furnace is making a "backfire" noise at end of cycle when it shuts off, what is that
Tim B on December 09, 2013:
In a new house and getting a tapping noise above ceiling in master bedroom when furnace for downstairs kicks on. Don't hear it when upstairs kicks on. Had a HVAC guy look at it, said unit is in very good shape, and he didn't know what the sounds are coming from. He said that he thinks it could be wood heating up and expanding/contracting. The thing is is it happens immediately when the furnace kicks on, lasts the entire time furnace is on, and lasts for five minutes after furnace kicks off. Sounds are very distracting when sleeping. Thanks!
Dan Reed (author) on December 04, 2013:
Hi MN Mike. Techs couldn't pinpoint the noise? Weird. That's what needs done. Air leaks can do this...they get so high pitched sometimes that you don't hear them during operation, like a dog whistle, but then as the fan slows, air slows and pitch changes to where you can hear. Perhaps motor bearings? Nearly 20 years...could be time for new motor? If so, upside is a new motor will save you on your electric bill. They are much more efficient these days.
minnesota mike on December 04, 2013:
Lennox G20Q3 75-3 furnace installed in 1995 is now making a high pitch whine just before final bloweer shut down.Filters are clean and several HCAV visits have failed to solve problem.
Dan Reed (author) on November 18, 2013:
Susan- space heaters are a different breed but yes. It sounds like metal expansion to me. There's not really anything else I can think would make that noise. Unfortunately, there's nothing I would feel comfortable recommending you do aside from securing something non-combustible to the metal plate to keep it from "oil canning". This would need to be done very carefully though preferably by someone who understands the dangers and/or damage that can happen if done improperly.
susan on November 18, 2013:
I have lived in my house for 30yrs. I have a space heater. T After the space heater starts and has been on for five minutes it will emit a very loud bang. It makes me jump every time. I don't use the on back of space heater, i cleaned it and it started to squeel. Could my bang be metal expansion?
Dan Reed (author) on November 05, 2013:
Well unfortunately if it's in the heat exchanger it will be tough to see, confirm or fix and may have to be lived with for the time being so long as the furnace is operating properly. There may be something loose in there that perhaps quiets down based on it temperature (becoming more pliable with heat) and it possibly stabilizing itself in the airflow as it stabilizes inside the cabinet. Sorry but this is a tough one that could be many things and though is annoying doesn't sound threatening. Make sure you have the exchanger checked for leaks just in case but if this was the exchanger itself I would think it apparent to the eye that the unit is in bad shape and needing replaced.
Paul klimowicz on November 04, 2013:
the problem with my old IGG furnace is that it rattles exactly 10 - 12 seconds after the furnace ignites, The rattles last for about 3-5 seconds and then quits, The rattle is a bit louder when the furnace comes on after the thermostat has just been raised, that is after the furnace has been off for a few hours, If it has been off for a few minutes, then the rattling is softer and shorter, I've taken the covers off and it still rattles, the noise seems to be coming from the heat exchanger but nothing seems loose, Any suggestions as to the cause and the cure?
Dan Reed (author) on October 27, 2013:
@ Jason Bryant - Okay so obviously check for any obstructions...perhaps a filter that is torn and getting hit by the fan or something like that however, it's more likely the motor's shaft is bent or the fan is loose on the shaft. If so, it would wobble in the "squirrel cage" and then sort of straighten itself out as it speeds up. If there is nothing in the way, this is what it must be. I'm not sure what type of furnace you have but if it's draft induced, then you have a smaller motor and fan near the chimney that could be the culprit. You may want to pull the chimney/flue off the unit and look down in that fan. I've seen where birds will get in there and cause this problem as well. Hope this helps and thanks for reading!
Jason Bryant on October 27, 2013:
Any time my gas furnace kicks on, the fan sounds like it's clicking against something and makes the loudest noise, but just until the fan is up to speed then it stops until the fan slows down at the end of cycle. Of course it makes a loud clicking noise again! Anyone that has some advice?
Dan Reed (author) on October 25, 2013:
@klm - Your situation is hard to diagnose in this manner however, the fan will come on by default when various problems occur. (not all, but many) If it thinks there may be a build up of gas as a result of ignition failure. If it thinks there is overheating it will use the fan to dissipate the heat. etc... In these cases though, the fan will only run for a predetermined period of time or to reach a setting and then shut off. It coming off and on and off and on is strange. Usually when there is a failure of some sort, the fan will come on as I described...then...(a modern furnace, 20 years or newer) will allow itself to try and restart. It will usually allow 3 failures in a row before going into a "lockout" for 1-3 hours and start over again. Each failure would result in the fan coming on before allowing a restart. So...start/failure/fan/pause, restart/failure/fan/pause, restart/failure/fan/lockout. I've described this so you can tell if there is a failure in the unit causing the fan to do this. A limit switches and thermostats themselves are common culprits considering the board has already been changed. I wouldn't be shocked to find the board is still a problem. Though not likely, it wouldn't be the first time I've seen a new board go bad quickly or even be bad out of the box. Could be a manufacturing problem that needs recalled and may never be. :-) You can learn more about what the actual problem is and what to tell your service tech by reading my hub here: https://dengarden.com/appliances/How-To-Figure-Out...
Sorry so long. Hope it helps and thanks for stopping by.
klm on October 25, 2013:
Our furnace motor is constantly turning on and off. We had our installers come and they cleaned the flame censor. That did not solve the problem only left us without heat and having to pay weekend rate and changing the electrical panel. Now this year it is beginning again. They guy came and cleaned the flame censor and left
Its back on and worse. Please help.
Dan Reed (author) on April 13, 2013:
That I am not sure. If it's only when your walking around perhaps it loose but that's a strange one. Mice? If you have insulated duct perhaps they're using the material to nest??? You've got me stumped I must admit.
vincent on April 06, 2013:
my ducts constantly make a rattleing noise even when the furnace is not running ...what could cause that?
Dan Reed (author) on March 07, 2013:
Well perhaps insulating the room is a better solution if the noise has continued beyond the first furnace. If both are as annoyingly loud then you may be right about the location of the utility room. Styrofoam boards can make a good noise insulator, be easy to work with and can be mounted to about any surface. Thank you for reading.
Dan Reed (author) on March 07, 2013:
@Bryce - Best thing is to check for loose parts, bolts or metal around the blower cabinet. If it's not something like that, replacement of the motor or mounts may be necessary. Thanks for reading.
Bryce on March 05, 2013:
Are the here an diy instructions for trying to fix a motor fan that s causing a loud rattling noise when the furnac runs? Every time the furnace kicks in I have to toggle with the circular fan cage and o stop I from rattling.
Cathrynliz on March 05, 2013:
I have a noisy fan attached to my furnace, but the old furnace was just as noisy. The furnace is in a small room in the center of the house. The hot water heater is there also, and the room is used for storage. The furnace has a metal exterior of course, and the pipes are all covered with what may be insulation. In any case they are wrapped in a shiny metallic looking cover. My theory is that the small room, which contains mostly metal and wood, is amplifying the noise. Do you think this is possible, and if so, what can I safely do to make the furnace quieter?
Dan Reed (author) on March 03, 2013:
@Heather - Well, the squeak you're describing is likely caused by either vibration or lack of return air that is creating a lot of suction inside the blower compartment. If vibration, you can try to use duct tape to quiet the noise (wouldn't worry too much about flames down there) or Crisco...may be more permanent than WD. As for suction, you may need more return air in your home. I can't begin where to tell you to add it since I'm not in your home but you could consult with someone about this possibility. Thanks for reading.
Heather on February 28, 2013:
Interesting and informative article! However, I was attracted to the "squeaky squeaky squeaky" in the introduction paragraph which doesn't appear to be addressed. The bottom front panel squeaks constantly while our furnace is running and it drives me bananas! I can't think of any semi-permanent lubricant (wd40 only works a short while) or non flammable cushioning material to prevent the friction. Do you have any ideas for me? Thanks!
Dan Reed (author) on February 04, 2013:
If the bang is before the blower comes on then this could be bad. You need to watch it as it lights next time and make sure that there's no abnormal firing inside the unit when the gas is introduced. A noise made by the rush of fire during start up isn't abnormal however the word "bang" makes me concerned if it's before the blower comes on. As for the "oil canning" of your ductwork when the blower comes on, you just need to pinpoint the spot that's popping and secure it by strapping a firmer piece of metal over the spot. Thanks for reading.
Luann Cutaiar on February 04, 2013:
Every time our furnace ignites, there is a very loud bang/rumble noise and then when its heated enough the blower comes on to heat the house. It doesn't happen again til the furnace ignites. It sounds like the venting blew out in an area, that sound of the sheet metal being sucked in and out. Real loud bumb
Dan Reed (author) on January 29, 2013:
Hmmm, this one could be a few things and to the imagination, a whole lot of things but...commonly, ducting can make noise as a result of a change in air pressure and/or temperature. Since this is a cold air duct, let's assume it's more pressure. The duct in your attic is resting (most likely insulated flex ducting in your case) when suddenly a fan kicks on sucking air through it like a straw. Once the pressure is stabilized, the noise stops. If I'm right, then perhaps adding some more cold air returns in the house can help. This will help reduce the amount of air going through any one duct thus reducing noise. Many will argue that a hvac system can never have too much air return for multiple reasons. Check as well for any loose fittings or pinched flexible ducting that could perhaps just used rearranged. Again, this is a guess and based on a common problem that exists in the industry.
Sorry so long. Thanks for reading and commenting.
pvolpone on January 29, 2013:
New 1 story home with furnace in attic. When the heat comes on there is this rattling clicking type noise coming from the cold air return in our bedroom it stops (sort of) after its running for awhile It wakes me up!
Dan Reed (author) on January 26, 2013:
Well, that's exactly what it is...a constant loud blowing. These are quite powerful fans in our furnaces. You may have a rather "average end" blower. There are some high end blowers out there that you could have installed and you wouldn't hear a thing. Check with a local contractor...perhaps an ECM type motor. It won't likely be cheap though.
Jean on January 24, 2013:
I hear my furnce when it comes on and more inportantly the entire time it is on. It sounds like I am in a maching shop. It it like a constant loud blowing. That is my unprofessioal opinion.
What is your professional opinion on the solution.
By the way, the house is all one level. No basement. This means the furnce is in the launry room. across from the bedroom and can be heard even with the door closed. Please advise. Thank you.
Dan Reed (author) on January 22, 2013:
@Della - Unfortunately, if you have what I think you do, it's just the fact that basically the blower is sitting in the room/hall with you. This is common in closet applications in order to pull enough return air for the fan. I doubt also that you have enough room on the return duct to add more returns elsewhere in the house which may not help anyhow since again, the blower is right there. It might not be the cheapest but the only real solution would be to purchase a ECM type blower that is super quiet when it runs. These aren't cheap but might be the only option for improvement.
Della on January 20, 2013:
I just moved in and have the loudest air return,in the hall that I have ever heard. The gas furnace is in a "closet" in the hall and the air return is not even 1 foot from the wall in the hall with the grate. I have the cheapest filter possible in it. I took the filter out and had the grate open and the loudness is directly from the furnace return. Is there anything I can do? It is so loud it effects every room in this little house! Thank you!
Dan Reed (author) on January 13, 2013:
@John Ingram - Booms? Pops? Ticks? Different sounds are different things. Crackling and popping could just be the sound of expanding metals. Bangs could be ducting. Booms could mean there is something happening upon ignition. Listen close and watch. Thanks for reading.
john ingram on January 12, 2013:
new oil burner loud at start up