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Air conditioner or heat pump noise diagnosis & cure: this air conditioning repair article discusses the diagnosis and repair of air conditioning compressor noises which range in importance from normal (if annoying squeaks and squeals, to rattling loose bolts and hardware, to costly compressor damage indicating air conditioning compressor or A/C compressors at or near end of their life. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. A/C & Heat Pump System Noise Diagnosis & Repair Noises: How to Diagnose Air Conditioner Compressor, Fan, Refrigerant Piping, Ductwork Noises
Possible causes of this particular A/C (heat pump) compressor start-up failure noise include
In the A/C system noise diagnosis article below we discuss how we approach listening to and interpreting noises coming from an air conditioning or heat pump system. CONTACT US by email to submit your own noise or noise+ video recording or if you cannot find the HVAC noise diagnosis information you need. If your air conditioning or heat pump system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS. See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. First question in diagnosing HVAC system noises is where are the noises coming from?:
Second question in diagnosing air conditioner or heat pump noises & sounds: what does the noise sound like?
Air Handler & Ductwork Noise Diagnosis & Cure for HVAC Systems
How to Diagnose & Fix Noises at the Compressor/Condenser & Condenser Fan UnitIf you hear unusual noise at the air conditioning system, these compressor sounds could indicate the need for a simple service and adjustment requirement. But air conditioner compressor noises might also mean that you face an upcoming costly repair involving replacement of the compressor itself. You should have the system checked promptly by an air conditioning service technician. The following is a list of air conditioning compressor noises and what they may mean about the operation, condition, and remaining life of the cooling system equipment.
Also See our Catalog of AIr Conditioner or Heat Pump Noises by Description of the Sound located just below. Also see NOISE, DUCT VIBRATION DAMPENERS and NOISE CONTROL for HEATING SYSTEMS where we describe duct noises. Fan noises on heating and air conditioning systems are discussed at FAN, AIR HANDLER BLOWER UNIT and at FAN, COMPRESSOR/CONDENSER UNIT. See NOISE / SOUND DIAGNOSIS & CURE for our complete list of building noise diagnosis & repair articles. How to Diagnose Noises at a Split System Air Conditioner / Heat Pump Indoor Wall-Mounted UnitFujitsu has offered some helpful advice in troubleshooting noises that may be heard at the indoor wall-mounted air handler of a split system air conditioner or heat pump. What's particularly helpful is that Fujitsu points out that some noises that people worry about are actually normal and not an indication of trouble. Quoting [3]
Here are some other noise or sound diagnostic clues for split system air conditioners & heat pumps
Frequently Asked Questions (FAQs) about air conditioning system noises: cause, significance, cure.We sort the reader questions and comments below alphabetically according to description of sounds coming from an air conditioner or heat pump system. But if you haven't already read our more general description of sources and types of air conditioning sounds and noises see the start of this article at AIR CONDITIONING & HEAT PUMP NOISES. Catalog of AIr Conditioner or Heat Pump Noises by Description of the SoundText Descriptions of A/C or heat pump sounds
Recordings of A/C or Heat Pump Sounds & Noises: Submit, Listen-to, or Comment on These Sounds
Question: Banging Sounds from A/C Compressor or Heat Pump, Frequent Compressor Replacements?OK. I just reread the instructions and it looks like I can ask a question. In the past 5 years we have replaced 4 compressors. We just replaced the last one and the fan motor. Every once in a while, the unit would make a repeated really loud banging sound as though some metal piece in the fan was whacking another piece over and over. Today I watched the clock. It is almost at every hour, but not at the same time. Each time the noise lasts 3-4 minutes. The A/C company and their electrician have no clue what this is. Also, the unit often trips the circuit breaker. Not necessarily when this noise comes on. We are incredibly frustrated. Any ideas as what could be causing this? Thank you. - Dina Reply: Dina, my OPINION is that if you are replacing compressors 4 times in 5 years something is drastically wrong. I can't guess whether the problem is an innate system design pressure, poor or damaged equipment being installed, or installation errors. But I share your frustration. I think it's time to talk candidly (but without threats or screaming) with the A/C company's service manager and to ask that they send someone who is trained and experienced to help diagnose this problem. And when you're told what problem was diagnosed, if you don't understand the explanation, ask for more help with understanding it until it makes sense. Follow-Up: Thank you so much. Here's the problem. We just changed service companies , because we were not satisfied that the old one was doing a good job. This one decided that the compressor and then the fan needed replacing. They've had two sets of technicians out here and neither could figure out the problem. There is nothing hitting the fan (so they say). The problem is that they are never here when the sound happens, though I did record the sound for them. They said it was nothing like anything they've heard before. They are coming out this morning again and we will see what they can find. Thank you for your "opinion". - Dina The tech was here again. He noticed that the last guy had installed a booster. He disconnected it to see if it helps. Meanwhile, I'm wondering if the noise has something to do with the unit working harder in the hot weather because I hadn't noticed the noise at all today and it's much more comfortable outside. I guess I won't know until it turns really hot again. - Dina Even with the booster disconnected, it's still making that banging metal sound. - Dina Reply: Dina if the banging clanging is a compressor noise see the article titled NOISES, COMPRESSOR CONDENSER Question: Bearing Noises in HVAC equipmentSounds like very loud bering noise on start up and shut down from a 1 year old heat pump compressor - Ray 12/5/11 Reply: Ray, a bearing noise, often a horrible clanking, banging, or rattling, is generated by a wobbling of a rotating shaft that is no longer evenly supported by bearings that are intended to permit it to rotate with minimal friction. If you hear bearing noises from an A/C compressor motor I suspect that the motor is failing, or that a similar noise is being made by damaged refrigerant valves in the compressor head. But first check that the motor mounts are secure. Sometimes a motor can make a clank or thunk at startup because one or more of its mounts has come loose. Question: Buzzing Sounds at Air Conditioner or Heat Pump & Buzzing noises after A/C cooling coil change-out, Diagnosis, RepairI had problems with my central unit freezing up and dripping water on my fan motor.. decided to have a technician change out my coil inside.. when he left my central unit outside starting making noises i never heard before.. my air conditioner kicks on inside first then after a couple of minutes it tries to kick on outside , it makes a loud noise then it runs finally and quiet like a central unit should run outside.. what is causing this all of a sudden, never had problems until he changed my coils out..not calling him back to my house. Bruce McCann Reply:HVAC compressor buzzing video: the HVAC noise diagnosis introduction near the top of this page includes a video example of brief buzzing at the fan/compressor outdoor unit along with some possible explanations. Below we discuss several A/C or heat pump compressor noise observations and possible explanations. Bruce, I am not clear on why a coil freeze-up indoors would lead to changing the outside coil - maybe low refrigerant or improper high side vs low side pressures? In any case, I would indeed give the service tech a call, tell him or her what you are observing, and give the technician an opportunity to return, see what's wrong, and fix it. Most technicians want their work to be correct and successful. Let us know what you're told - it will surely help other readers. Question: Buzzing sounds from air conditionerMy outside fan motor is running but the unit makes a loud buzzing noise every few minutes or so, the motor was replaced last spring. I sprayed the motor shaft with wd40 just to get me by till I can get another fan motor if that is needed. I do not know if the capacitor was replaced or not. the loud buzz only lasts for a few seconds then stops, I just turned the unit back on, Any ideas on what I can do or a place to find a motor?- Rodney Looney Compressor started producing a buzzer noise which lasted about 4 seconds then stopped and repeated again. The time between buzzes varied from a 10 to 20 seconds. The noise reminded me of the sound you hear on the radio when they do there check of the emergency broadcast system. - Jim I have a Trane 4 ton gas pack that is making a intermittent buzzing noise when the compressor operates. We are located in Phoenix, AZ and the noise seems to have started this season when temps heated to 100 and above. Naturally, I'm concerned that this might be compressor noise since the unit was manufactured and installed before the AC season in 1994. Thanks for any suggestions you can offer. Doug The noise pattern may be different from when I first noticed it. I checked the pressures, for the first time since we got the house 8 years ago and and added 4 lbs of R-22 to get it back to normal operating conditions at 95F. The performance isn't noticeably different, but the noise pattern may have changed somewhat, while the sound is about the same, when it does occur. Reply: Buzzing Sounds at an A/C or Heat Pump System May Mean Failing Electrical PartsRodney: if you need a new condenser fan motor you should be able to match the original by taking the old one to your local HVAC supplier, or you can probably find a replacement online. I'd be sure you note the motor information and specs from it's data tags or just bring in the old motor to your supplier. Watch out - don't keep replacing motors unnecessarily. A bad fan motor contactor relay or even a loose wire could also cause buzzing in the condenser/compressor unit outdoors. . Jim: sounds like your compressor is having trouble starting up? Or does it buzz but run ok otherwise? Doug, buzzing sounds from an air conditioning component might be a failing electrical component and could involve even a fire risk; I'd try to track down more carefully where the buzzing is occurring. A burned compressor contactor relay, for example, might buzz. Follow up: Dan, Follow up: Dan, I was looking around another site and the owner mentioned that the compressor suspension mechanism can break and cause noise that sounds like a bad bearing. A friend of mine knows a person in the refrigeration business and after my friend described the problem, he said it sounded like a broken spring in the compressor suspension. I guess I am going to have to replace the compressor before the start of the next season, if I make it through this one. The compressor has rotolock connections, and I would like to avoid any cutting/sweating operation if I can reasonably-safely avoid it. Thanks for your help. - Doug Reply: Doug: Follow-Up: Dan, I found a video on You Tube that shows disassembly of a compressor like mine. I don't think there is a broken suspension, but I would believe bearing noise. I don't understand how it can be so intermittent. Under certain conditions, something resonates and makes a real racket. Dan, Reply: Doug we see filter dryers installed at both sides of the compressor. It depends ... if a system is thought to be contaminated there are advantages of having a filter at both ends of the compressor motor, and it certainly doesn't hurt. - DF Question: A/C System Buzzing noises for 2 seconds, bad start/run capacitor? Outdoor unit makes a buzzing noise for about 2 seconds & stops. Fan never starts turning. I was standing by unit when this happened for the third time & manually started fan turning. We seem to have traced this A/C buzzing noise to a bad start/run capacitor - Hill Question: Clanking Noises, Clunks, Thunks, Shoes in the Clothes Dryer: Sounds from A/C CompressorThe home A/c unit at start of a cycle sounds as if a pair of shoes are in the dryer, what may cause this noise? - Frank hi, my ac works good, but it makes a clanking noise. Could one of the bands be loose? - Celia Cisneros Our compressor makes noise before it gets running. What might this be? - Edison I'm in Texas in the middle of a record drought\heat. AC is doing pretty good despite the heat (takes it a while to cool back down but it's 108 outside). However, when the system shuts down I do hear a thunk inside, not so much outside. No sound when it starts up. Also, we had a couple of surges a few weeks ago and the fan outside is running a little bit louder. I'm *really* hoping everything is just working harder because of the heat. - Mom My air conditioner unit outside makes a ungodly noise that just started this morning at 2 am. My husband said he saw that the fan is missing a blade and that is why it is shaking and making the noise I keep hearing when it kicks on. it sounds like an air compressor that my cousin uses when he uses his air tools.. please help me know if this is able to be fixed or should i start buying window units...? ... Now the fan has stopped completely but we can still hear the motor running. Heather 11 yr old air conditioner works fine, but is makes a continuous rattle and a loud clung when shutting off. It's driving me, and I think my neighbors, crazy. - Ruth Reply: Loose motor mounts, Loose Fan Parts and Ticks, Clanks, Clunks and Vibrations in the Air Conditioner or Heat PumpMom: that inside "thunk" sound in your A/C air handler could be a loose blower fan assembly or mount - I'd have someone take a look before it gets bad enough to cause more damage or stop working entirely. Keep us posted - what you find will help other readers. Heather: Ruth, rattling and a Clunk when the compressor/condenser shuts off sounds like loose parts, maybe even a loose compressor motor mount or loose fan parts or both. I would have the system checked immediately as the risk is that something comes loose enough to cause expensive or dangerous damage to the system. Note that if the clanking or rumbling noise is coming from a blower fan motor the cause could be bad fan motor bearings. Questions: Clicking Sounds, Air Conditioner that won't stop, Rapid Clicking Noises, Humming Click every 20 secondsHi. The outdoor compressor of my central air conditioner will not stop automatically. Everything else operates properly. The fan for the outdoor compressor turns on and off properly and all the indoor components operate properly. Any ideas what I can do to fix this? - Bruce So, the air conditioner in our apartment works perfectly ...turns on when it should, and turns off when it should. The only problem is that when it turns off, there is a really rapid clicking noise that sounds like a metallic plastic noise. If you were to take a circuit breaker, and turn it on and off REALLY fast, you would get an idea of what it sounds like. Other than this, the AC unit functions perfectly fine. Any ideas? Thanks for this awesome site! - Adam My a/c condenser is not working, the fan blades do not turn, when I lower the indoor thermostat and then go out doors to the condenser pad, I hear " a humming click" approximately every twenty seconds or so, as if the unit is trying to turn on. Reply: Ron: Question: rapid clicking noise in air conditionerSo, the air conditioner in our apartment works perfectly ...turns on when it should, and turns off when it should. The only problem is that when it turns off, there is a really rapid clicking noise that sounds like a metallic plastic noise. If you were to take a circuit breaker, and turn it on and off REALLY fast, you would get an idea of what it sounds like. Other than this, the AC unit functions perfectly fine. Any ideas? Thanks for this awesome site! - Adam Reply: Adam, if the noise continues as long as the unit is on, I'd look for a loose blower fan whose blades are hitting something, or an obstruction that has fallen into the fan path. There are switches or controls that can also click, but I figure a problem in one of those components means it's going to give up the ghost soon- things will stop running and the system will have diagnosed itself. Question: Condenser or Blower Fan Noises: rattle, hum, or speed-dependentQuestion: we had a power outage this morn, for about four hours, after which previously fine HVAC came back on making an awful racket ...sounded like blades were hitting something, but i shut it down and searched and that was not the case ...bearings? it is chilly hereabout and I am wondering if bearing froze up or some such and that things will get back to normal as day gets warmer...any help greatly appreciated...it is a Trane. - Rattle 1/16/12 Question: Just had the blower motor replaced to our 14 year old Carrier. Now the blower sounds normal when the furnace is on but when the heat pump kicks on it is extremely loud sounding resonating through the house like the washer on it's final spin cycle. The technician said that our motor has two speeds. One for the furnace (lower speed) and one for the heat pump (higher). Funny that the system didn't make these noises before the blower motor burned out. Any suggestions. I read through many of your pages but not being a technician failed to find an exact or suggested cause. Could it be something with the heat pump outside, itself? - Peter 3/22/12 Reply: Fan rattles are often traced to a bad fan shaft bearing or fan motor mount that's loose; on occasion we also hear a ticking or snipping sound when fan blades are hitting an obstruction (wire, stick, something else) either because something has intruded into the fan blade path, or because the fan blade has come loose on the shaft and is hitting the protective cage or other internal components. A hum from the fan motor in either compressor/condenser unit or in the air handler/blower unit is often traced to a hard-starting fan motor. Replacing the start/run capacitor can sometimes help cure this trouble. When a multiple speed or variable speed fan is installed in HVAC equipment, a rattle or noise may show up only at the [more stressful] hire speed, especially if the problem is a rattle caused by a combination of a failed bearing or fan mount and blades that are bent or out of balance. Question: Growling or Groaning Noises from the CompressorQuestion: Hi, My home compressor is quiet when first started but makes a growling sound for a few seconds every time it starts after. I did add a hard start kit but it still growls. - John Reply: John: that growling A/C compressor noise at startup sounds like a hard-starting compressor; when a hard start kit fails to correct the problem, I'm worried that the compressor is shot. A service technician can diagnose the system and answer that question more reliably; typically s/he will start by measuring the amps drawn by the motor as it starts. High amps = end of life. Question: Hissing Sounds from the Heat Pump or A/C System, Diagnose, RepairHissing sound and humming from my AC - It was the capacitor! Thanks! - Bingo Question: Hissing Compressor noises, ice on the suction line, hissing ssssss sounds from air conditionersir i check my out door unit i see the compressor is getting cold and after few minutes the amperes will going up start in 17 up to 20amp.,and it comes sound like noise, yes that was my compressor also, din after few minutes suck line becomes ice and noise coming like ssssssssssssssssssssssssssssssssssssssssss..... - Danny Carumba
Question: Hissing in "surround sound" after installing a new high efficiency A/C and Heating SystemI have a very high pitch hissing sound "surround sound" throughout the whole condo. We did install a new /better/efficient AC/heating system...some original duct and tubing is still in place. The problem is, we can't sleep with this noise! And cannot pinpoint where its's coming from: wall. I need a professional with GOOD hearing to hear this. We will be putting some sound proofing on the garage back wall that abuts, unfortunately the condo (6 units attached) doghouse. We have had all items on the wall of the doghouse shut off and can STILL hear this high pitch hissing? Any suggestions to what we can do and WHO to contact? Have had 2 electricians, and audiologist, etc. check this but their hearing is not like mine and I do not have tinnitis, because when out and about I hear fine and not the hissing. HELP please. I really don't want to move. - El Reply: Track down sound source before installing soundproofing around an A/C or heat pump systemEl, before installing soundproofing it makes sense to track down the source of the annoying noise - especially since the noise, if abnormal, could indicate failing or even unsafe equipment that needs repair. We discussed hissing at the compressor condenser unit above at Hissing or Screaming A/C compressor, but not all hissing is due to extreme pressure. An A/C or heat pump compressor (of the reciprocating or piston and cylinder design) that continues to run with damaged internal refrigerant valves may make a hissing noise too. In this case the motor will continue to run, it may not even overheat, but it's wasting electricity and running more than it should. An HVAC tech may diagnose bad A/C compressor valves by noticing that the high and low side pressures equalize very quickly when the motor stops. Hi Dan ...thank you for responding to my question ....I cannot track down the source...it's Surround sound....everywhere....not emanating from one spot unfortunately! I do live in a condo setting, had the Condo president shut off all electrical items in the doghouse: housing of the electrical, pumps, phone, etc ...shutdown could still hear the noise! It seems no one can hear this ...except my family and none of us are in a business to locate the source. We do have all underground lights, no poles ....I have tried earplugs even, I don't have tinnitis, because when I am not inside the condo...no problem. Electricians and even PSNH don't seem to hear the very high pitch noise. If I could locate the source: one spot ...I would gladly put a hole there. I think until everyone else's' stuff starts breaking down so we can get a 5 for 1 deal this won't be fixed...and I know at this point the original builder is probably past the taking to court stage. Contractors who worked on these? To pass code IMO ...barely. Any sources or websites you can suggest I'd appreciate. Thank you. EL I would also like to mention that a Large PSNH box sits at the end of our driveway....they opened it up and changes a plug of sorts (???) not sure what, but also, a lot of underground cables under our particular front yard:PSNH, cable ...etc. it would cost a lot know it would cost a lot , but don't feel we should have to pay since it (source)unknown still ....is the cause. We also, have to contact Dig Safe prior to planting.. .I would think that the cable's, etc. would be way under , at least 4 or so feet...does anyone know building codes on cable depth necessary to pass codes in NH? If so please post here and info. as to contacts:web page , phone numbers, etc...it seems to have increased as far as sound over the past 4-5yrs. We have also had a PSNH person come out to our condo to check our meter and it says with limits of Section PUC 304.02 by NHP Utilities (NHPUC), Chapter PUC 300, rules and reg's for electric utilities .....really ...I feel like I've exhausted my resources and I am not in this field...any thoughts to help? - El. Reply: El, beginning at NOISE / SOUND DIAGNOSIS & CURE we organize some approaches to trying to track down odd sounds. To get anywhere with public officials or electricians they will of course need to either hear the sound themselves or confirm it with instruments. Question: Hissing sound traced to a bad capacitor?Hissing sound and humming from my AC - It was the capacitor! Thanks! - Bingo Question: Hissing at compressor/condenser unit in hot weather, heavy load or after 5 minutesI have a carrier 2000, don't know how many tons it is but here's the problem; I had a few hot days above 100 with abnormally high humidity. I turned on the AC in the early morning when it was relatively cool. It ran for 3 days straight with no issues. Then I noticed the air wasn't cool at all. Just warm and humid. I went outside to investigate... The condenser was making an obnoxious humming and it sounded like the compressor had a blow of valve. It was hissing like it had a leak with a large amount of pressure behind it. I waited a couple days to turn it back on. It started fine the condenser sounded good and the fan started like it should and it was finally pumping out cold air. 5 minutes go by. I hear the loud humming again and the hissing. So here is my question: Is my compressor shot or am I low on freon. Because it will over heat and shut down. Thanks for your help. Reply: Aaron: "The condenser was making an obnoxious humming and it sounded like the compressor had a blow of valve. It was hissing like it had a leak with a large amount of pressure behind it." suggests an overpressure at the compressor, perhaps a blocked condensing coil or dryer. Your system needs service, but the compressor is not necessarily shot - let us know what your tech says. Follow-up: Dan: Thanks for the tip. By doing some research (and I am no HVAC guy by any means) I found that the compressor would indeed over heat because of too much pressure. I looked at the a coil in the furnace itself and it looked fine. I don't however understand " the dryer" factor. I did wash the outside of the unit before i started it and the air filter is spotless. Reply: Aaron: if there is an overpressure at the compressor, a cause is usually a blockage somewhere. I don't know all possible causes, but some examples are Question: Groaning, Huffing, Compressor making Wuw, Wuw, Wuw sounds or wa-wa-wa sounds or wow wow wow sounds or Huffing & Puffing Sounds: examples, diagnosis, repair adviceQuestion: Thanks for posting this -- it's been helpful to read! My question: The fan runs fine on our AC unit, but the compressor makes a slow, thrummy, WuwWuwWuw sound about every 30 seconds, as if it's trying to start up but can't, and there's no cold air coming out of our vents. I'm not sure if this is the same as the "humming" described above. Is it possible that this is caused by a loose connection or faulty capacitor? Or should I assume that it's something more serious? - Tiny Question: Ours has a different sound outside: a sort of huffing and puffing. We only hear it after the unit has been running for a long time. Any ideas? - Herbert Lewis Question: I saw the q&a about the wow-wow-wow sound but no answer other than tell us what you found. I have had it since it was installed but the heat pump tech said it was normal. I know it was not but gave up. Now it's bothering me more. Any new/better answers? The wow cycle period is about one second - in radar search antennas we used to call it "hunting." (for the right speed). There it had to do with control feedback settings, but somehow that doesn't translate to a heat pump unless it means too much coolant. Could that be it? - Dick, 3/11/2012 Reply: Huffing Puffing wawa or wowwow A/C Units - still and open question, how to investigateHerbert: huffing and puffing is a new one to me: an air conditioner compressor making this noise might be reaching an overpressure condition due to a control failure or blockage - let us know what your HVAC tech diagnoses - it will surely help other readers Sometimes the wowwow sound is from a compressor that is hard-starting. In that case you are hearing the electric motor trying to start against head pressure (or against a binding internal part), perhaps cycling on and off. Dick, thanks for the question. We're very serious about developing a dictionary of sounds and their diagnosis and cure; but sometimes, especially by text, I just don't quite know what a sound is or even quite what it sounds like. The wowwow is one of those I'm unsure about in that there are several causes and several sounds that people describe as wowwow wawa. But in this FAQ (just above and continued below) we include some possible explanations and will add others as they crop up. An on-site an expert might observe something cycling (as you describe) that helps track down the problem. For example, if you used a mechanic's stethoscope and tracked the sound to a specific part that is emitting the sound (probably a compressor or maybe a thermostatic expansion valve, on occasion a fan motor or bearing) then once we know where the sound is coming from, we can dig into what might cause that part to do that. For example a part on a system may be making a sound not because that part is itself defective but due to another control. Reader follow-up: The sound is LOUD and must be from the compressor itself and passed along via the tubing.. The compressor is outside on the ground level and it is distracting on the floor above (beach house on stilts). Here are some added steps to take to track down a sound to its exact source - a first step in diagnosing sounds
Reply: Hard Starting A/C and Heat Pump Compressors May Make Groans, Wuw, and WaWa or Wah-Wah-Wah- SoundsTiny, it sounds as if your A/C compressor is indeed having trouble starting; It makes sense to be sure all wiring connections are secure (Watch out for electrocution shock hazards) but I suspect you need a hard-start/run capacitor kit. I would leave the system OFF until it is repaired. And keep in mind that a hard-starting compressor may be at/near end of its life. Thanks so much for that input. I've been trying to decide whether it's worth having someone come out to check the capacitor, and it sounds like it might be. I'm not really prepared to pay to replace the compressor or the whole unit this summer, especially since I'm up in Canada, so the A/C is more like a luxury than a necessity. Thanks again! - Tiny Reply: check for bad start capacitor;I think it's worth checking for a bad start/run capacitor because if that's the problem it's an inexpensive part and avoids someone selling you a compressor condenser unit that you probably didn't need. Also a bad motor winding can cause similar complaints. Question: Humming Noise from A/C SystemI have a 13 year old Armstrong AC, 4 ton, 10 S.E.E.R. in our house. For the past 5 years (ever since we got into the house), the outdoor compressor unit has been making loud humming sound. The sound does not sound like humming if I stand next to the compressor unit outside. However, inside the house, the sound is of humming. The AC has worked fine - no leaks, cools properly etc. I have had it serviced but every time the service person chalks the noise to age and recommended a new AC w/o any investigation. It could be just age but I'd welcome suggestions things I can check for myself. I followed the two lines (thin copper line and the larger/covered in black line) running between outdoor and indoor AC units. If I put my ear next to the larger line, I can clearly hear the humming sound along its length as I move from the outdoor AC unit to the indoor condenser unit. I can also feel vibrations/tremors on this larger line. I have been hearing a humming when my air conditioner is running now for about a week but the air is cool and working o.k. but this is coming from the compressor outside and wondered what it could be??? - Joyce Ballard There is a humming noise coming from the Heat Pump AC unit when the thermostat is in the cool setting, but the thermostat is set below room temperature (air conditioner not running). If I move the switch on the thermostat to the off position the humming stops in the unit. Do you have any idea what is wrong? Thanks, Don 6/3/12 Hi, I live on the second floor of a condo and hear a loud constant low pitched humming noise coming from inside the wall where the tubing enters the unit from the outside and travels up the wall and across the ceiling to the internal blower. The sound is not present when the heat is on. It is a deep harmonic mmmm sound and has a vibration component. The AC blows cold and otherwise seems to be working. The compressor is 10 years old. - Barbara Rich 4/9/12 Reply: Pinning down the exact humming noise source on HVAC equipment: refrigerant line noise transmission, loose component parts, low voltage transformers, and hard starting -electric motorsA humming noise that you are hearing at the larger refrigerant line (the suction or "low pressure" line) can help you trace the noise to its source: the indoor air handler or the outdoor compressor-condenser. Knowing the source can help track down a detail that may or may not be repairable, such as a loose part, loose compressor mount, or worn out compressor internal parts. Watch out: a humming noise coming from an electric motor or A/C - Heat Pump compressor motor that is not actually starting and running is likely to indicate that the motor is unable to start, and is at risk of overheating or damage. Humming from a motor that can't start is sometimes repaired by replacing a bad start/run capacitor, but if the motor is actually failing and seizing, it will need replacement. Humming sounds are also given out by a low voltage transformer that is headed for failure. Question: Condenser not working, humming soundsMy a/c condenser is not working, the fan blades do not turn, when I lower the indoor thermostat and then go out doors to the condenser pad, I hear " a humming click" approximately every twenty seconds or so, as if the unit is trying to turn on. Reply: Hilary it sounds as if you are describing a hard-starting or stuck compressor motor. The click you hear may be the the result of the system turning itself off (unable to start) followed by a cool-down interval, and then the system tries again. You need a diagnostic service call and if in luck it could be a a bad start capacitor. Out of luck, a shot compressor. Other problems can also cause the compressor to have trouble starting, such as a bad refrigerant control valve. Question: Loud Noises at Startup, then Quiet Compressorhi, i had problems with my central unit freezing up and dripping water on my fan motor.. decided to have a technician change out my coil inside.. when he left my central unit outside starting making noises i never heard before.. my air conditioner kicks on inside first then after a couple of minutes it tries to kick on outside , it makes a loud noise then it runs finally and quiet like a central unit should run outside.. what is causing this all of a sudden, never had problems until he changed my coils out..not calling him back to my house.. Bruce McCann Reply: Indoor coil freeze up vs outdoor sounds??I am not clear on why a coil freeze-up indoors would lead to changing the outside coil - maybe low refrigerant or improper high side vs low side pressures? In any case, I would indeed give the service tech a call, tell him or her what you are observing, and give the technician an opportunity to return, see what's wrong, and fix it. Most technicians want their work to be correct and successful. Let us know what you're told - it will surely help other readers. Question: Air Conditioner or Heat Pump Popping or "popcorn" sounds - Warning!Question: a/c condenser unit sounds like a popcorn machine only when going off Question: I just had a new compressor installed outside two weeks ago. In the last few day this unit has emitted loud intermittent "popping" sounds like firecrackers that keep us and the neighbors from sleeping! Cannot see anything obvious and not sure if related to recent repair. It is not a regular pattern or a metallic sound. Recorded for our a/c guy and he thinks a wire is loose and the sound is an electrical contact sound. Ideas? Thanks. Mike C. 9/12/11 Reply: Watch out: an A/C or heat pump compressor motor that is receiving liquid refrigerant on the suction or intake side of the system can make a popping noise or popcorn noise - and is at serious risk of becoming damaged or destroyed. Liquid refrigerant should be found only on the output side of the compressor/condenser unit not at the compressor intake. Causes of "liquid flooding" of an HVACR compressor include improper refrigerant charge (too much refrigerant) or a malfunctioning refrigerant metering device at the cooling coil. You should shut off the system immediately and leave it off until an experienced HVAC service tech has diagnosed the problem, hoping that we might avoid destroying the compressor motor. Other causes of popping or knocking sounds in air conditioners or heat pumps - knocking sounds can mean a bad motor bearing, bad motor mount, or on occasion, a spinning fan blade hitting a component in either the air handler or outside in the compressor/condenser unit. In automotive A/C systems, condensate dripping onto a hot exhaust manifold can also cause a "popping" sound in some designs. Watch out: electrical shorts and loose wires can also make a "popping" sound at any electrical equipment. Turn off the equipment to reduce the risk of a fire or dangerous electrical shock. Any readers with other suggestions please post a "popcorn noise" comment. Question: A/C or Heat Pump Compressor Rattling & Vibration NoisesQuestion: We just noticed our outdoor compressor unit running noisier than usual. Not exactly a rattling noise but a louder than usual buzzing type sound. It was constant. So we turned off the AC at the thermostat. and looked around the unit to see if we could see anything unusual. Didn't really know what we were looking for, but didn't see anything unusual. About 15 minutes later we turned the AC back on and it took about 10 minutes to "kick in" at that time there was only a low humming sound from the compressor. The fan never started. We let it run for about 15 minutes and there was no change. Just prior to noticing the noise in the first place, we realized that it seemed hotter than it should be in the house and the air blowing out of the registers was room temp, not cool. - Kim Well, I read the story below about the person who was told to rinse off their external coils. so we gave that a try while the AC was turned on. After about 3 minutes of spraying with the garden hose it started up. It sounded smooth, too, no strange noise, except for the water spraying off the fan blades. YAY! Well Darn it. When we woke up it wasn't running again. I got it started again by spraying with the hose. But the whole system doesn't seem to be blowing as cold as it used to. And my guess is on the next cycle the compressor wont start on it's own again. - Kim Question: Refrigerant floodback noises - running water or gurgling sounds in the refrigeration pipingI have a 4 ton heat pump that hisses when it shuts down in 40* weather. The frig. lines run in the wall near bedroom. Sounds like freon running back to or from compressor, Only in heat cycle. - richdunegan@gamil.com 12/11/11 Question: Just this morning I noticed when my heat unit/pump was running it sound as if water was draining through pipes. (The out side connections to the pump/inside unit run over head in my laundry room) So far there's been no other issues. Any idea what this could be? Should I be concerned? Once the heat shuts off this draining sound quits. - Ruth 1/25/12 Reply: Refrigerant floodback noise can occur at any time not just at startup. A severely overcharged system compressor can have floodback when running and this can lead to compressor failure from oil being flushed from compressor or broken valves in reciprocal compressors. - Tommy 1/15/2012 Ruth, also check for running water sounds traced to drain piping that receives air conditioner or heat pump condensate from a condensate pump. Because the condensate pump only runs when its reservoir is filled, the pump on-off cycle will be irregular, but the pump may be sending water into a building drain that, because of its material (plastic) and location (not through sound-insulated space) could show up as a running water or gurgling sound. Question: Regular cycles of A/C noises every 30 seconds, Vibration SoundsAC has an intermittent loud vibration that lasts about 15 seconds and goes away. It occurs about every 30 seconds or so. We just had to have freon installed because the unit was running but never able to achieve the set point. We keep it at 76, so it wasn't like we were straining it. My husband is checking to see if it's level right now since we read a comment that out of level can lead to vibration and from there to a refrigerant leak. We obviously had a leak since the gas was at less than half of its required level. - Rebecca Reply: Cycling or repetitive noises in HVAC compressorsRebecca: there are several failures that can cause a frequent cycling noise in HVAC compressors such as Reply: Rattling, followed by Low Humming Noises and hard starting compressors Kim: that humming sound makes me think your compressor is either suffering hard starting or is at end of life and close to seizing. Question: Silent or normal noise A/C Compressor - still to be replaced?My AC is blowing warm air. Everything is in working order except the technician found a leak from one of the tubes coming out of compressor closer to the unit itself. He told me that the whole compressor would have to be changed. Is it true? The compressor sounds normal. - Ehab Reply:blowing warm air ... lost refrigerant; I answered this question just a minute ago - maybe on our refrigerant gauges page? Ask him/her why you need a new compressor instead of a fix of the refrigerant leak and either a recharge, or if your refrigerant is an obsolete R12 or R22, why not use a substitute refrigerant?Note that a compressor may sound normal or even close to silent but be running but may not be pumping refrigerant. If this is the case the unit has broken internal parts and needs replacement. A symptom would be no refrigerant pressure difference between high side and los side lines even with the compressor "running". Question: Singing or rumbling compressor/condenser unit noisesSounds like a whining, singing or rumbling sound coming from the compressor/condenser unit fan motor may be due to a broken internal cooling fan motor part or a vibration set up between the fan blade and fan motor/shaft. Question: Squealing A/C or Heat Pump Compressorsour compressor started squealing intermittently the other night around 1:30am. Did it for about 2 hours but not consistently nor constantly. drove us and the dogs crazy. hasn't done it since. HVAC tech says it was the compressor bearings and can't fix it since its 20 year old unit. I think that's love. what do you say? - Secn Reply: Normal vs abnormal squealing sounds at A/C compressors Secn: ... "that's love"... is that a new term for B. S. ?? Anyway, there are multiple possible sources of squealing, such as the compressor motor, or even a fan motor. If it's the compressor, it's dead or dying; because the units are hermetically sealed, they're not repairable. Follow-Up: Thanks Dan. yep, wonderful spell check changed from the word I had originally typed to "love". it was a clean word though but B. S. works just as well. hah aha. So, the tech also said it's drawing high amps along with the bad compressor. Would the cap fix this too? He said he can't service anything on it Cruz it is R22 freon and can't be obtained anymore. I know they are moving to the R410a but I still say B. S. - Secn Reply: Sorry Secn but high amps draw means the motor is near end of life. The cap may keep it going a while but it sounds like it's bad news. Tech is also right about the refrigerant. You may be able to install a new compressor, evacuating and cleaning the system (better to do it BEFORE a compressor burnup as a burnup contaminates the piping and increases the later repair cost a bit), installing a new compressor and a substitute refrigerant, possibly having to make some other adjustments, but less costly than a wholesale replacement. Keep us posted. - DJF Question: Wow Wow WaWa or WuW sounds from an A/C or heat pump systemPlease see Question Groaning Huffing - earlier in this list. Question: can you tell us what the attached air conditioner sound recording means?Attached is a few seconds of the noise made by our Kenmore air conditioner/heat pump, when the propellers start turning, about 10 seconds into the recording. It was much worse in the winter with the heat pump, so we heated with oil only. It was so bad, the house rattled inside. The compressor and motor were replaced a few months ago, but the noise persisted and the maintenance company gave up after eight visits. When the weather got hot, we decided to give the air conditioner a try. The air conditioner was working without us noticing any noise but now we can hear it, as you can tell from the recording. What can we do? Your help would be greatly appreciated. - L.G. Reply:Honestly, I'm not dead certain, but the sound we heard in your recording sounded like a mix of buzzing and rattling. I've heard sounds similar to this from both a failing crankshaft in a motor and from an air conditioner compressor that was liquid slugged with refrigerant due either to an improper charge or a malfunctioning refrigerant metering device. I have two suggestions: a technician, using a mechanic's stethoscope, ought to be able to pinpoint this noise to the offending part or motor. If the noise is traced to the compressor motor I suspect my guess above is not far off. It is possible that once the system has been running for enough time the noise may fade as the compressor has pushed the refrigerant out to the high side of the system. Watch out: liquid refrigerant slugging of a compressor motor is a problem that occurs on the low pressure side of the system where the equipment is designed only to move refrigerant as a gas, not a liquid - liquid slugging of refrigerant at the compressor motor is likely to destroy it. I hope you've already eliminated more obvious external rattles such as a bad bearing or motor shaft or fan blade ticking against screen or internal component. At Recordings of A/C or heat pump sounds & noises we have introduced a new HVAC diagnostic feature (thanks to you) where we posted this air conditioner sound recording to permit other readers or experts to offer comments. ... Ask a Question or Search InspectApediaQuestions & answers or comments about air conditioning or heat pump system equipment or control or ductwork noises: cause, significance, cure. Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one. Click to Show or Hide Citations & References
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