HVAC units produce unexpected rattling noises
Multiple users are experiencing unusual rattling or loud sounds coming from their HVAC systems, both new and existing. They seek advice on identifying the cause and potential solutions, ranging from DIY fixes to professional assistance.
SOURCES (60)
“Recently moved into this rental and the AC just started screaming at me! I tried turning it off for a bit and as soon as it turned back on it started screaming again. I have no idea what I’m looking at and was wondering if…”
“For the past few weeks, I’ve been hearing this strange crackling/scratching sound coming from inside the wall whenever the A/C is running. It seems to happen mostly when we’ve had heavy rain. We’ve already had electricians check the wiring and A/C connections, but nothing unusual was found. If anyone has experienced a similar issue or knows what could be causing this sound, I’d really appreciate any ideas. Video attached for reference. submitted by /u/DutyTemporary4595 [link] [”
“Been having this rattle for a while, I’ve looked around online trying to find out what it is but I can’t find out whatever I search for or how long. Sounds like it’s coming beneath the foam but how would I even go on about fixing this rattle? Putting pressure on the foam lowers the rattle but it’s been coming more frequent, or I just start giving it more notice. Have had the car for 4 months, I love it but this sound is driving me insane. It’s a Audi A3 combi 2021 8Y. Please anyone with experien”
“The AC is actually working fine, I have it running on low-power (~800W) dehumidifier mode maintaining about 27 C. It's been running basically 24/7 since June 2026. This is during monsoon/summer season in India in a concrete/brick house. Brand: 1.5ton Midea split inverter AC Location: Goa, India The complaint: Over the past month, the indoor fan unit has started making a gentle rustling noise, like wind blowing through leaves but somewhat lower pitch. It happens whether the outdoor compressor”
“My minisplit has been making this sputtering noise. Any advice? It does speed up and slow down with the fan speed. submitted by /u/DarkKnightAKABatman [link] [comments]”
“Basically title. I got a 12,000 BTU and a 9,000 BTU installed. Fujitsu. The 12,000 BTU unit, while in cool mode, always has a very feint "russling" type sound. In heat mode, the only sound you hear is the air flow. In cool mode, it's air flow plus this other sound. I really don't know how to describe the sound. It is not a rattle. It does not sound like parts hitting eachother, or a vibration. The best way I can describe the sound is like, a computer hard drive in a desktop PC”
“Hello all. Noticed a couple of things that need some care and was looking for input. First pic is of the brittle piece of condensate line. 2nd pic shows the type of insulation I need. 1) I have a mini split with water pump condensate that goes up to the roof and drains into the gutter. The condensate line is very brittle and broke off toward the roof. I know I should replace the whole line but can't manage that right now. Question is, what type of tube should I buy to extend that is good for”
“Wife noticed this yesterday, but we're not sure how long it's been doing it. Came with the house that was built in 2018. 18F differential at the AC filter intake and exhaust temp. Panel was off as I was checking the capacitor and contactor to make sure they were working. Says this on the side of the unit: PROD CA15NA03600GAAAA MODEL CA15NA036 - A Thanks!! FYI, I changed the capacitor about two months ago, as the original one went bad, and now that I think about it, it was also making the”
“What causes this? Happens rarely but from time to time on Lennox units. It’s from the compressor. Been told several different things. submitted by /u/Dump_Truck_Wallace [link] [comments]”
“Hello, long post here, thanks in advance for reading. I had an American Standard s9v2c100d5psc furnace installed in my house last summer that is a communicating system with a heat pump. I believe it is a 5 ton 100,000 btu unit in a 2 story + basement 2400 sq foot house. Initially the installers put an incorrect furnace in, had to reorder from the warehouse, then installed the correct furnace but making a mistake of leaving a large piece of duct over the box it sits on, blocking at least a third”
“I have new Carrier AC 3 ton unit for 1350 sq ft. It has been running great for two months. About four days ago something strange started happening. The first cycle of the day only lasts 2 minutes. Then the rest of the cycles are normal. Except yesterday the first cycle was normal. The filter looks okay (2 months old). Does anyone have an idea what it might be? I understand that usual short cyling occurs repeatedly whereas mine doesnt. submitted by /u/coffee-linux [link] [commen”
“Our hvac just made a sound like a saw blade wobbling as it was pulled back through the cut, or a ruler on the edge of a table and pulled back. What could have made this sound. submitted by /u/SoundsFun2Me [link] [comments]”
“Anybody know what’s causing this? It still makes the sound when the ac unit is turned off. submitted by /u/Key_Grapefruit_4227 [link] [comments]”
“My basement flooded and got right up into the blower motor area. I was able to dry it out and put it back in. However I was hearing this humming sound from vents. So I just replaced the capacitor on the blower motor. The humming stopped for a couple minutes. Now I can hear a faint humming sound next to furnace and thru vents again . Not as loud as before. When I’ve checked the blower motor. The motor is gets a little warm but not hot to touch. I’m able to spin it without and resistance. I took a”
“My AC external unit was tearing into some cheap rubber gasket sold as anti-vibration thingy! Time to 3d print some proper support: ABS shell and 20% infill TPU core. Works as intended. submitted by /u/Elderberry-Mediocre [link] [comments]”
“Does anyone know what this noise could be? It keeps happening while the AC is on. It sounds like a creaky floor or bed. submitted by /u/Evening_Strawberry50 [link] [comments]”
“As it says in the title, I need some help muffling the vibrations coming from my portable AC. Long story short, I didn’t realize the vibrations coming from my portable AC when the condenser kicks in could be such a loud sound disturbance to downstairs neighbors. I would like my neighbor to stop scaring my cats by banging on the floor so loud it shakes. I currently have it on 1 in of foam (the puzzle kind), a spare wooden shelf I can’t use anymore, then .55 in of the same foam, and then a blanket”
“when we run the heat it gets up to temperature, then it makes this low humming sound until it comes on again. Normal for these, or something needs to be serviced maybe? submitted by /u/OkBox3637 [link] [comments]”
“I had a new mini-split installed this summer and now that I've switched it to heat mode, it's making a loud popping/cracking sound about every minute or two. It's quite annoying as I can't sleep well because of it. I noticed the unit has quite a bit of play if I grab it and try to lift it slightly (see the other video in the comments). My other unit in the living room is rock solid and completely silent. Could this thermal expansion/contraction noise be caused by a loose mounting”
“Long story short: Neighbor’s AC unit is transmitting a vibration/noise into my house. Tried putting those square rubber/cork pads between the housing and concrete slab…no change. Just realized that maybe the vibration is still transmitting via the metal hurricane brackets that connect the housing to the slab. Wondering what the best way to dampen that would be between the brackets and ac housing (don’t want to have to undo/redrill the tapcons into the slab to dampen it there). Neoprene washers o”
“Had a guy install a Della mini split in my room last month using a wall bracket. It cools well, but when it’s running really hard, I can lowkey feel a hum through the wall. It’s not too loud, just annoying when I sleep. There are some rubber pads under it. Is that normal for a wall mount, or should I move it to the ground? submitted by /u/LongjumpingRushS [link] [comments]”
“Hello all. Can anyone diagnose what is wrong with my condenser? Basically, it stops working at random and starts making this sound, while the fan stops spinning. The weird thing is that it always eventually fixes itself. Normally I just have to turn the breaker off for an hour or so and it will go back to normal. One time I even kicked the unit and the fan started running again. I've had HVAC guys out multiple times, but by the time they get out to my house, the unit is running normally and”
“My neighbor’s condenser fan sounds like it is trying to explode and I’d love to be a good neighbor to help guide them toward a solution so they know what to ask for quotes to repair. it’s been making this noise for weeks and only getting louder. It also happens to be right outside my bedroom window and is becoming very annoying so the more I can encourage them to fix it the better. Is this as simple as loose screws or is something like a bearing shot? Unit can’t be older than 8 years old since t”
“Anyone know what this sound could mean? submitted by /u/BlackMagicTurtle [link] [comments]”
“I installed a new transformer on my Lennox air handler and when my system came back on it ran for about an hour then my condenser started rattling still blowing cold air but then it blew the new transformer big time what is happening submitted by /u/Royal_Celebration_67 [link] [comments]”
“Our AC stopped blowing cold air three days ago, just replaced the capacitor today, does it sound like it’s running correctly? submitted by /u/thmmk [link] [comments]”
“Unit was a little rattle-y. Last time a tech was out here he just tightened up some stuff on top and it was much quieter. Tried to do the same and snapped these guys off (the second one was because I am stupid). Is this easily fixable, or did I create a big repair job? submitted by /u/theTAUSonMangoSt [link] [comments]”
“We bought our home in April 2025. It has a Goodman Hi Efficiency HVAC gas furnace air conditioning unit purchased in 1993 (written date on original manual came with home). It’s been working great since we’ve had our home. I clean the white air intake often (and have since I took the video). We live in West Texas where it’s a desert. We’ve had no rain with a bad drought and we have had SO MUCH DIRT this year. I vacuum all the time. I wipe things down all the time. We have three indoor cats &”
“I have been in a bit of a battle with my builder about what I feel is excessive noise from the condenser. I am in a new construction neighborhood, and the unit is placed right outside of the primary bedroom, directly behind the window. The placement is definitely not ideal. I have been in several other houses in the neighborhood, same floor plan and unit location, and none seem to be this loud. I would have sworn the noise was coming from within the wall, but after cutting open the portion that”
“Got a new 4 ton unit installed a few days ago and when it turns off it makes this grinding sound every time. Called the HVAC tech and he said it's normal but I'm not so sure. It's functioning perfectly fine otherwise. submitted by /u/LeBrownJames405 [link] [comments]”
“When my outside unit turns on, I hear a consistent popping sound inside the interior wall where the unit is. I do not hear the sound outside where the unit is. Only on the inside; when the unit is off the noise stops. The unit was installed 2 years ago. Edit to add unit is cooling normally. submitted by /u/Forsaken-Seesaw-1362 [link] [comments]”
“Last month I had my 3y old AC unit replaced under warranty after a failed coil and failed compressor. They agreed to put a new outdoor unit in and swap the indoor coil. Since then the temp is fine but when the unit kicks on or off I can here it no matter where I am in the house. It’s a surge of energy as it starts and stops. Today for the first time sitting under a vent when it kicked on I noticed a wet/damp/moldy smell coming from the vent in the air. The house is only three years old - and thi”
“My AC now has a nice rattle to it. I have one upstairs and did a quick jiggle test to see if everything in the cabinet was secure. The fan spun freely with no resistance. The motor seems secure. Do I need to just pull it out and do a better check? Any steps to diagnose would be great. Yes I know i still have drywall work to do. Video is for sound only. Thanks for the help. Any suggestions would be helpful. HVAC guy is days out and I can change a part if needed. submitted by /u/BuyitO”
“Hi! I’m a new homeowner and am a nervous Nelly about big ticket items. The HVAC unit is 2017 and has been taken care of as best as I can tell. I haven’t noticed this before and I haven’t been able to find another video online. Anything to look into further? Thank you!! EDIT: it’s a Trane XL16i submitted by /u/Trick-Kitchen626 [link] [comments]”
“This contractor is making noise, it starts when the damn circuit breaker tripps. Any ideas? I have already changed the capacitor. submitted by /u/Shoddy_Equipment_983 [link] [comments]”
“tl;dr: the a/c is making this harder run sound/warbled sound as described by my tenant only at night, not during the day and the house is warming a bit. more detail: this house is was build in 2017 and was the model home/sales (re: no one lived in) unit until 2020 when my husband i moved in. we lived there thru 2024. never a single issue with the house. we've had the same tenants in now since Aug 2024 and this summer the a/c has been driving me mad. it wasn't cooling, so we had a full di”
“Boiler makes this random loud zapping/clattering noise. Very hard to locate since it happens every few hours. I eventually caught it on camera shown in the link. I thought it was chatter so I replaced the contacts but that didn't fix it. Any help would be appreciated. submitted by /u/boiler_troubles [link] [comments]”
“Cooling just fine. Unit is 5 months old. submitted by /u/DifficultySoft9742 [link] [comments]”
“I experienced a similar problem with it a few months ago, the noise wasn’t as loud, but eventually led to leaking and having to have the pipe replaced as well as the drywall. it has been a month since the repair in the same noise as happening again, but louder. I also saw a quick electronic message where the temperature usually is but it was so quick I didn’t see what it said. I turned the cooling off and kept the AC on and after 12 hours it would still make this noise on and off. The only way t”
“I have a ~8 year old Two Stage Rheem HVAC system with gas furnace. I recently noticed that there is a constant noise coming from Evaporator and/or refrigerant line. It seems to constantly cycle, and change its tone, almost how a shaving cream can would sound different as it gets close to empty. My Rheem certified tech says it's normal, but I can hear this a floor away, and this noise was not there when the system was new. All diagnostics are good and there are no errors on our communicating”
“Sound when fan kicks off. I’ve spun the blades and they don’t seem to rub on anything. Fan itself didn’t seem loose either. submitted by /u/Mid-Delsmoker [link] [comments]”
“A couple months ago, my closest neighbors replaced their package heat pump. The new one wakes me up with a loud rumbling sound each morning between 4 and 5 am. This is much louder than the sound it makes when operating at other times of day. It is currently very hot where I live, so their heat pump must always be in cooling mode, even at night. It seems like the heat pump is operating on a schedule and doing something specific between 4 and 5 am each morning. It sounds like a diesel truck idling”
“I’m living in a shared student apartment with several bedrooms. There are two outdoor air conditioning units, one is right outside my window, it causes some vibration, but not too much. However, the unit outside the neighboring room’s window causes intense vibration whenever someone in the apartment turns on their AC. It seems the noise is loudest in my room, I’ve asked the others, and they say they can hear it too, but not very loudly. The vibration seems to travel through the wall, it’s a low-”
“It starts normally, then after a while makes this loud noise. If I turn it off for a bit and re-start it, it is fine for a bit then starts again. submitted by /u/TheyRLying2U [link] [comments]”
“I recently bought a Mobilcomfort 6000 BTU window saddle AC to replace my portable AC. Part of the appeal was that it's supposed to be really quiet since the inverter sits outside. Yet it gets loud when this buzzing happens, and then goes quiet when it's just the fan. I checked and it doesn't seem to be my window that's vibrating, but genuinely the AC itself. I'm not quite sure if this is normal, or if I should return this? It's only been 2 weeks since I bought it so I sho”
“Few months ago it was making this noise when running after 5-10 min, just had maintenance done on it a month prior and everything checked out well. It was set to 72 inside and actual temp was 80 so it wasn’t cooling. I shut the system off for 24 hours and had a guy come back and look at it. The noise went away and everything read normal again. He said he thinks it’s the compressor and wanted to replace it all for over ten grand. I decided to wait it out and its been running normal but since its”
“My AC started making this noise that comes in waves. It's kinda quiet in the video but its actually pretty loud and obvious. Im not sure how to describe, it is kinda like grinding. Can anyone help me figure it out? The fan seems to to spin fine so I don't think it's fan bearings submitted by /u/thonfused [link] [comments]”
“Hello everyone, wanted to see if I could get some advice for my scenario. I have a Day and Night 4 Ton Condenser from 2016 that started squealing. At first I noticed the fan also wasn't running so we replaced the capacitor and fan motor to be safe but the squealing continued. Turns out it was the compressor squealing intermittently and loudly during operation. My HVAC guy did some measurements of the voltages and checked the pressure levels but unfortunately concluded that it's most like”
“Hello everyone. I am just anxious if this sound is normal or not. This is in my daughter’s bedroom. The rest of the house doesn’t have this noise though. submitted by /u/Mayas_world [link] [comments]”
“This has been making noise I got home from work. How do I fix it submitted by /u/TheGreatAbernacky [link] [comments]”
“Does anyone know why it makes that sound, and how I could bring it up to management? That noise at night keeps me from sleeping peacefully. submitted by /u/Jewister [link] [comments]”
“Listen the sound and help me with your expertise. Thank you! submitted by /u/Vast_Armadillo_2188 [link] [comments]”
“Attached is a video of it happening, moved in to this house a week ago, please advise! submitted by /u/___next [link] [comments]”
“See the red arrow. I can't tell if this is an HVAC unit (AC maybe?) that's been toppled over, or that's just the way it looks when installed. It's also weird how there seems to be black wires that go nowhere. Any help with figuring out what's going on? submitted by /u/helpfuldunk [link] [comments]”
“Hey everyone- Just had a brand new two-stage Carrier Performance unit installed and it’s been great so far. Something that seems to be slightly alarming is that whenever the unit cuts on it lets out a rather loud burping sound. The frequency and duration seem to vary wildly, sometimes less than a second to over 3. This is followed by, I assume, the lines pressurizing which is almost a bubbling sound, and it has been getting more noticeable lately. I had the installer come take a look, and they s”
“It’s 6 years old, and cools great. It seems to sound normal other than the startup. Any thoughts on this? Is it normal? It seems loud and harsh submitted by /u/RsCyous [link] [comments]”