HVAC compressors make buzzing or rattling noises

“I have a buzzing noise coming from my AC in the attic. It’s off and on but pretty frequent. What could be going on? TIA! submitted by /u/Ok-Market6989 [link] [comments]”

“2025 RUUD Endeavor with R434b refrigerant. I asked about this before with heat mode, but I've noticed it also does it in AC mode if the temp is below 65ish degrees outside. When it's warmer than that and you can't really hear it starting up at all. Why would the cooler temps make it sound like that when it starts up but not when it's warmer? Is there anything I can do to make it quieter? You can hear it like 3 houses down, so imagine how loud it is in my living room right next to”

“I have a 2016, 3-ton, 16.5-SEER Trane XR unit that appears not to be cooling. After I checked it, I noticed the indoor side still draws air, but the outdoor fan does not spin. I heard a buzzing noise and am attaching the video. For now, I've turned off the thermostat because I don't want to damage it further. https://youtube.com/shorts/nJocoVHgB8I?feature=share I am wondering how I should investigate this. Is it most likely the capacitor, and should I just ask for it to be changed? I rep”

“https://imgur.com/I2xHMAe (I tried uploading it as regular Reddit video but it kept failing) In SoFlo. My balcony AC compressor has been making this noise since this morning seemingly whenever it has been powered on. I havent noticed it was coming from here until now. It is always this loud when the compressor is on (zero noise when just air handler fan is on). I have already called my technician to check it out but I'm still curious what this could be? Bearing failure? Fan scraping? Somethi”

“Just moved in - HVAC guy comes to do a furnace tune up. Turns off the breaker to the air handler to service the furnace, but when he flipped the breaker back on, the AC compressor started, ran for a minute then shut off. Hmm. I went to the thermostat, set it to cool, AC came on a usual and ran fine. So…the thermostat was set to heat when this happened. If I understand correctly, the compressor comes on when a 24v signal goes out to the unit and says “hello”. Sort of… Do I have a bad thermostat,”

“Hello! I'm new here. This central unit AC started making humming sound last night. I checked the condenser and circuit breaker. Everything is still on and working. No air coming out of the vents. I'm assuming that the fan is not working? What could be the cause and how to fix it? Thanks yall submitted by /u/Severe-Vermicelli311 [link] [comments]”

“My aging compressor motor began producing a metallic grinding sound from a worn bearing, so I lubricated the shaft and it has returned to normal for the time being. I will likely need to replace it soon, but I am wondering whether this noise level is typical or if a new motor would reduce the sound. submitted by /u/todesto [link] [comments]”

“My aging compressor motor began producing a metallic grinding sound from a worn bearing, so I lubricated the shaft and it has returned to normal for the time being. I will likely need to replace it soon, but I am wondering whether this noise level is typical or if a new motor would reduce the sound. submitted by /u/todesto [link] [comments]”

Working on this reefer van, found a kink in the Pipe, fixed it with a hydraulic hose, but the compressor makes a disgusting crackling noise, changed the filters because the pressure was…

“We turned on our heater for the first time this season and around 15-20 min in, it started making a loud buzzing sound. I didn't open the panel but did take a video, any suggestions/thoughts/advice would be helpful! The heater isn't that old and it's not too cold outside (~50F) so we just left it off for now. Hopefully it's not a terrible issue! submitted by /u/MarsupialNo2450 [link] [comments]”

“I keep hearing this humming noise (see video) on and off while the AC is on. It’s been running a lot because we’re in the middle of a heat wave in CA so I was thinking maybe it’s because of that but is it something to be concerned about? submitted by /u/meangreengingmachine [link] [comments]”

“This is a short video of a loud buzzing noise my Thermo Pride oil furnace is making after it finishes a cycle. I’m guessing it makes this noise around 10-15 minutes afterwards then is quiet until the next finished cycle. This started at the end of the season when I had it serviced with an annual cleaning in late Spring. The noise seemed to go away when I first noticed it then of course I stopped using it for the Summer. When I started using it very recently just a few days ago there wasn‘t a noi”

“History: Lennox unit and it is only 5 years old. 8 months ago we had duct work replaced and the concrete pad under the unit leveled. Immediately after, we started hearing this noise and the technician said the TPX valve had failed causing the compressor to go bad so we had the compressor replaced. It worked fine until this past week. It started making this noise again and we lost AC. Technician checked Freon levels and they were fine. He checked capacitor and said it was fine. Yesterday he insta”

“Hello everyone, I present to you my 2007 Goodman GSC130301AD unit, equipped with the Copeland CR23K7-PFV-230 Hermetic (Reciprocating) A/C compressor. As of last night it sounds absolutely awful, I have never heard it sound like this in the 3 years of owning it (I have not owned this unit since brand new) and so I went to shut it off last night and I didn’t start it up until this morning, and first try this morning it sounded normal, smooth A/C compressor buzz and fan blend, then I shut it off an”

“Dealing with noise from a neighbor’s outdoor compressor coming through my house. Easiest solution I can think of is adding a compressor blanket (and maybe cleaning the coils) to reduce the noise at the source. I’ve already put vibration pads under the unit (which didn’t do anything), and now I’m fairly certain the noise is air bound. Would a compressor blanket reduce a 130 Hz pulsing hum at all? submitted by /u/antiramie [link] [comments]”

“I’ve been using this AC for almost 3 years now, and I honestly never really bothered by the sound. I either didn’t notice it at first or I just got used to it and it became white noise to me. But whenever someone comes into my room, they always point out how noisy the AC is. I’ve been running it 24/7 and only clean it every 6 months. Is this kind of noise normal for this brand/model? The sound in the video is a bit exaggerated compared to how it sounds in person. In person, it’s actually pretty”

“When the ac starts, it makes a loud sound. It is always loud. If i go up to it, I see the fan inside barely moving. It just started an hour ago.. how can i troubleshoot this? submitted by /u/Virtual_Treacle_9158 [link] [comments]”

“Just had a compressor replaced on my 5ton straight cool Bryant 410a system and noticed the new compressor starts making a buzzing sound, but only when outdoor temps are above ~85f. This is driving my OCD crazy. System cools fine otherwise. Attached is a video I took on 90 degree day of the condenser starting up...you can begin to hear the buzzing at about the 42 second mark. Im assuming when the head pressure gets above a certain level it puts more strain on the compressor, but is this something”

“Sorry for reposting, I accidentally didnt include the video in my first post a few minutes ago. The sound happens around 5 seconds and then 55 seconds into the video. There is some intermittent clicking throughout but I couldn't tell if it was from raindrops or coming from the condensor. https://imgur.com/a/DkZGTWf submitted by /u/kittyvanilla [link] [comments]”

Sorry for the late post and dark video. I just got home from a work trip and while I was walking up to my front door I heard the AC unit kick…

“A couple weeks ago HVAC replaced a coil in my AC unit (after a bad smell was coming from my vents). The smell is gone, but now I get this motor sound ever since that replacement (about 2 weeks ago). Today is the worst it’s ever sounded. Luckily I shut my AC off for the season after hearing this sound, but want to see if anyone knows why my AC is making this sound? submitted by /u/Isittheweekend [link] [comments]”

“Hi everyone, would really appreciate some help diagnosing this! There’s a strange sound coming from the AC unit (see video with sound on) it’s like a buzzing / vibrating noise? The room is on the second floor, and the AC unit is outside on the first floor, basically I look out the window and down at the first floor and it’s right there. Whats weird is that when I go outside, stand right beside the unit and listen, I don’t hear this noise. I also don’t hear the noise from the first floor window t”

“Last night when I was sleeping the compressor started vibrating very loudly and would turn off every 3 minutes. I turned it off the rest of the night and this morning it’ll make this intermittent humming noise but won’t shut off. What could be causing this and will it be a hassle since it’s a through the wall? submitted by /u/ScrambledHuevos [link] [comments]”

“Had a new air conditioner installed on 8/24. It's running fine. But tonight as I was taking the trash out I noticed this sound above the normal low hum. Is this something we should contact the hvac installer to come look at? I have no experience but to me it sounds like something with the blades spinning. Sorry for the shitty lack of light. No lighting on side of house where ac is. submitted by /u/thrawn819 [link] [comments]”

“Someone help! I serviced my AC unit and now the compressor is making weird sounds. Yes I removed the power before servicing. I used coil spray and water. Any help would be appreciated. Trane XR Model 4TTR5036N1000AA. 3 years old. submitted by /u/plencoolilikeplen [link] [comments]”

submitted by /u/RGV9562025 [link] [comments]

“Howdy folks. Last night my AC shut off. I noticed a pretty nasty electrical “buzzing” sound coming from the inside unit downstairs. The buzzing would last approximately 15-30 seconds before shutting off. A few minutes later, this would repeat. I replaced the capacitor, and it kicked back on but the buzzing was constant while the blower motor was running. It then began to slowly turn off, as if the RPM’s of the motor were slowing down until it stopped. Later that night, it completely stopped work”

“The compressor occasionally makes this noise. Got it looked at by a HVAC company and they said they couldn’t replicate it and could not find anything wrong. submitted by /u/CincyScaper [link] [comments]”

“It’s been hot in San Diego, and so our AC has been on almost constantly. Both the indoor blower/furnace and outdoor condenser were replaced about 2 years ago. Since last night, there has been a loud hum/buzz sound coming from the blower cabinet, easily stopped with a gentle smack. Any ideas? Video with audio below https://imgur.com/a/w4EaC01 submitted by /u/GSEninja [link] [comments]”

“Anyone have any ideas? The fan did not just finish running. The fan doesn't kick on right after the noise stops. The noise goes on for about 3 minutes before it slowly fades away. It seems to happen randomly. AC appears to be working fine. The house stays cool, no problem. submitted by /u/k_bangers [link] [comments]”

“My AC wall unit is constantly making this noise when off. Even if I go a full weekend without being home and having the AC on, I’ll come home and it’ll be making this loud humming noise. It’s incredibly noisy and does not sound like something that should be happening, especially after just sitting there for days. What is it, and how can I suggest to fix it? Apartment living, so it’ll be a maintenance call. Just want to make sure this isn’t normal submitted by /u/catstacker [link] &#3”

“Noticed this a few days ago but hasn’t gone away. If I push down on one of the corners of the cover it dissipates a bit but the oscillating sound doesn’t go away. I know nothing about HVAC, but the fan seems balanced at a glance. Something sounds like it’s vibrating. Should I be worried? I’m going to call my HVAC guy tomorrow and get him out asap. Everything is cooling fine. I tightened down all the outside screws that I could. submitted by /u/South_Paw_1988 [link] [comments]”

“Last night the AC was running but every few minutes it would buzz and the fan would slow and then continue. Shut it off and this morning found this. Read up on here and discharged and replaced(trimmed wire and replaced connector as well). AC is up and running now thankfully. My question is do new capacitors need a little charge or something like that? Reason being, when I replaced it, the first time the fan turned on for a few seconds then shut off. Turned thermostat and breakers on and off and”

“This is a Honda city GM6 model , just now my boss change this car compressor and condenser. This noise appear when we turn on AC but after we turn off AC this noise disappear. submitted by /u/This_Diver_9032 [link] [comments]”

“The sound only happens when it’s turned off. It works well despite this issue. However the sound is driving me crazy and had to switch off the breaker. MSZ-SF25VE Can I solve this by myself? If not how much will it cost? submitted by /u/MassiveBlackout [link] [comments]”

“A few months ago our blower motor kicked the bucket and started making a buzzing sound. We had an emergency hvac company come by and replace the blower motor and capacitor. A few weeks later there was a mechanical hum/vibration that would progressively get worse and was never there before. I could hear it through the whole house and it started driving me crazy. We called the company back and they came to take another look. Said it was our squirrel cage was caked with dust and was likely causing”

“That’s my compressor turning on and sometimes it’ll bring my idle down a ton when it turns on, I’ve been told it sounds bad but wanted more opinions. 1993 Toyota celica at180 submitted by /u/Substantial-Bear-292 [link] [comments]”

“Fan spins Not blowing cold air Replaced capacitor but keep hearing this noise Is it end of life of compressor, is it low on refrigerant? HAC236AKA5 model HQ1086646AX capacitor Thanks in advance submitted by /u/SpaceGuy9990 [link] [comments]”

“Condenser is making this odd noise, I wouldn’t call it a grinding noise. Context, it’s a 13yr old system, just had the compressed replaced about 4 months ago. submitted by /u/nabiscosoursnac [link] [comments]”

“Anxious homeowner here… is this the sound of refrigerant leaking from the coil? AC is holding temp just fine at 74. It was over 90 today in Chicago suburbs. I see no ice buildup on the coil or on the unit outside. The unit wasn’t running during the video. Should I shut off the AC? submitted by /u/soupy56 [link] [comments]”

“hi, starting tonight we have been hearing this very loud humming/buzzing noise that will go for up to a minute and then stop and then start again maybe 10 minutes later or so. I recorded the noise and linked it below. It seems like it's coming from the big metal column in the middle (I'm sorry I'm very uneducated about this stuff!). Can anyone please tell me what this is and how I'd go about fixing it ? thank you! https://voca.ro/1l1hvLL0A0RC submitted by /u/Insta-tai”

“So I started noticing my lights dim every 2 minutes along with a buzz while the AC is on. (Fan is running, but the air isn't super cold). The same buzz, which lasts for about 3 seconds, occurs at the outside unit while the fan is running. This doesn't happen exclusively, but happens in the middle of the day for an hour or so and then the air will blow normally and the buzzing doesn't occur. We just had a tech out but the issue wasn't happening while he was here so he said everyth”

“Something in our furnace is making a loud whirring/whining noise when our AC is running. Based on Google search it seems to be bearings or rotors, parts of the blower motor. Still runs properly and blows cold air thank goodness (in TX). I have an HVAC tech coming out on Saturday (two days from now). Should I worry something could get worse but then? Tech didn’t seem too concerned on the phone. Edit: some extra info, it sometimes sounds louder/worse than others. Sometimes it doesn’t happen at all”

“Posted a video the other day but in this video much easier to hear, description below: If you listen closely, it almost sounds like a very light hissing noise then it’ll randomly make what almost sounds like metal rattling. I’ve never heard an AC make a noise like this. Some back story: Due to severe condensate issues, eventually the HVAC tech replaced the coil (whole system was only 9 months old) a week or so ago. I noticed it made this weird noise maybe a few days after the new coil installati”

“I recently had a new Carrier Performance 2-stage compressor installed by a reputable installer. I’ve read that quality of installation is just as important as the actual equipment, so we spent a good amount on this. I’m attaching a video of the hum it gives off. It’s just high enough that it drills into my brain! I don’t mind the buzzing, but it’s the hum that I can’t live with. Could anyone familiar with Carriers let me know if this is normal? I’d be grateful for the input. Thank you! sub”

“My HVAC unit started making this sound in the middle of the night. The only way to stop the noise is to cut the power, turning off has no impact. It’s a Mitsubishi Electric, maybe 6 months old. Any help would be much appreciated! submitted by /u/Time-Eye5402 [link] [comments]”

“I’ve had this Trane ac unit for less than two years and it’s now making continuous loud noise, an electrical humming sound. It used to only make that sound when the ac compressor was starting up, but now it makes a the sound continuously while running. No noise while off. Our AC Tech said capacitator is fine, pressure is fine, Freon levels normal, what can this problem be? Do I need to send the whole unit back to Trane? submitted by /u/Top_Entertainer7501 [link] [comments]”

“It takes a couple seconds to start. In addition to the rattle on the outside. Increased humming from the insides during the rattle. This is a Ducane, newly installed last June. Our HVAC guy said they replaced a capacitor but the problem persists and they're not returning calls. I'd like to have an idea of how to direct the next professional that comes out. submitted by /u/Traditional_Split_51 [link] [comments]”

“My a/c on start up hums loudly, but once it’s running it’s nice and quiet, fan spins freely and isn’t seized/ bearing seems good. Is the capacitor bad or going bad or is this normal for an older unit ? submitted by /u/coolguyry18 [link] [comments]”

“Hey everyone, hope all is well. I heard this coming from my unit and wanted to see if it sounds like a loose piece or if I should try to further trouble shoot. Ac is running normal and I did a basic cleaning of the unit with a hose the other day that involved taking the fan off. Not a tech or anything, just a basic diy guy. submitted by /u/Then_Inspection9750 [link] [comments]”

“My outside AC unit is making weird sound when it turned off.. Sounds like motors are running backward when it stops. My HVAC installer says it's OK. But I don't trust them. This is less then two years old unit. Still in warranty. Any idea? submitted by /u/wsb_desi [link] [comments]”

“System Context & Setup: Residential split-system AC outdoor unit. Replaced a failed dual-run capacitor. The replacement got the compressor and fan starting right up again without issue. The Problem: Cooling performance: The unit cools effectively—indoor vents blow ice-cold air, heat exhausts properly outside, and it successfully pulled the house down from 75°F to ~73°F. The Noise: At lower indoor temperatures (around 72°F–73°F) or after extended runtimes, the outdoor unit develops a heavy, l”

“If you listen closely, it almost sounds like a very light hissing noise then it’ll randomly make what almost sounds like metal rattling. I’ve never heard an AC make a noise like this. Some back story: Due to severe condensate issues, eventually the HVAC tech replaced the coil (whole system was only 9 months old) a week or so ago. I noticed it made this weird noise maybe a few days after the new coil installation, but I was finally able to capture it on video. What does this sound like to you? &#”

“Hello everyone. I recorded a short video of the noise my outdoor AC unit has recently started making and would really appreciate some help identifying what might be causing it. Unit is only 1 year old The noise started a couple of weeks ago. We did not have this issue earlier in the summer. It only happens when the AC shuts off automatically after reaching the thermostat temperature . If I manually turn the AC off using the thermostat, the noise does not occur. The noise is brief but fairly loud”

“New homeowner here, I know it’s a general sound but I can’t seem to find where it’s coming from on the unit. Everything appears to be running fine but it’s the only unit of 3 making that noise. submitted by /u/Responsible-Scar896 [link] [comments]”

“First video: When my central AC kicks on the outside unit has been making this sound, it is coming from the fan. when the fan/unit turns off as the fan slows down it kind of sounds like when you sharpen a knife. Like two metal pieces just scraping against each other. Can anyone tell me what’s going on? I’ll see if I can fix it otherwise I’ll cough up the service call but I’m hoping not to since money is tight atm submitted by /u/johnjohnsee [link] [comments]”

“Just found out mine is louder and We have the same model. Is mine about to die? submitted by /u/fucyuman [link] [comments]”

“Condo HVAC is making this sound when cool is on. And was also reported to make a low whistling sound when only fan on. What could the problem here? Thanks for the help! submitted by /u/holaworldanna [link] [comments]”

submitted by /u/red_deadRT509 [link] [comments]