HVAC Noise Diagnosis & Cure: How to Evaluate Air Conditioner / Heat Pump Compressor, Air Handler, Ductwork Noises InspectAPedia® -
How to diagnose & repair air conditioning compressor noises
Diagnose & repair air conditioning system noises: compressor, fans, air handler, ductwork
Air conditioner buzzing may be just a loose part
Air conditioner humming, clanking, buzzing noises can indicate a minor or a serious problem - it depends ...
AIr conditioner or heat pump noises may diagnose lost cooling capacity
Air conditioner or heat pump noises may predict equipment damage
Air conditioner compressor defect diagnosis
Questions & answers about air conditioning system noises: cause, significance, 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.
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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.
Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
A/C & Heat Pump System Noise Diagnosis & Repair NOISES - How to Diagnose Air Conditioner Compressor, Fan, Refrigerant Piping, Ductwork Noises
Start tracking down the cause (and cure) of noises from your air conditioning or heat pump system by listening carefully to determine the location of the sound.
Our first question in diagnosing HVAC system noises is:
are the sounds from the compressor/condenser unit located outdoors,
from the air handler/cooling unit located indoors, or
from ductwork not necessarily near either of those components?
or is the noise somewhere else and perhaps from another source.
Air Handler & Ductwork Noise Diagnosis & Cure for HVAC Systems
Air handler / blower indoor cooling unit noises: see air leaks, bubbling, clicking, duct noises, fan noises and vibration dampener noises and the articles on these problems listed just below.
Air leaks in ductwork often make a roaring or hissing sound. See LEAKY DUCT CONNECTIONS and also see VIBRATION DAMPENERS for a discussion of devices used to isolate noises produced by HVAC air handlers such as air conditioners and furnaces.
Buzzing sounds (also crackling) at electrical components anywhere, including compressor relay switches, electrical connections at any component, and quite seriously, at circuit breakers can be an indication of arcing and an electrical problem needing prompt attention. See Electrical System Noises
Clicking noises from relays & controls can be heard at either the compressor/condenser or at the indoor air handler unit: A failing or defective thermostat or to a defective control itself can cause relays to click on and off repeatedly - see CONTACTOR RELAY DIAGNOSIS & REPAIR. Thanks to reader Michael Anderson.
Clicking, rumbling, ticking, rattling, clang and clunk at startup: loose hardware are detailed too at COMPRESSOR CONDENSER NOISE
Clicking and ticking sounds at HVAC equipment are also traced to a loose or bent fan blade hitting an obstruction. See FAN NOISES
Compressor/Condenser units: see NOISES, COMPRESSOR CONDENSER [just below] for detailed diagnostic help in finding, evaluating, and fixing noisy compressor units. Humming, rattling, explosion noises, bangs, clanks, hissing, squeaks, humming, squealing noises.
DUCT SYSTEM Noises: hisses, whistles, even roars, and occasionally clunk or clank sounds from expanding or contracting metal ductwork. We may trace these sounds to supply ducts, return ducts, registers, to a bad vibration dampener, or other components.
Animals in the ductwork can make a variety of sounds, depending on the critter: fluttering and clanging (a trapped bird), scratching and gnawing (squirrel, mouse, rat, raccoon), buzzing humming (bees or wasps). See ANIMAL ENTRY POINTS in buildings.
Blower assembly and fan noises might be transmitted through the air ducts, such as fan squeaking, squealing, rattling. See FAN NOISES
Return air leaks: Leaks around the return air register are common and sometimes noisy, perhaps due to a poorly-fit air filter or gasket - see RETURN DUCT AIR LEAKS. See Take a look at LEAKY DUCT CONNECTIONS. Also see our more general article on Air Leak Noises
Supply air leaks: Hisses and whistles in supply air ducts and registers might be present too - see SUPPLY DUCT AIR LEAKS.
Transmitted duct sounds: Also buzzing, rattling, clanking or other noises originating at the air handler/blower unit may be transmitted into the physical ductwork and thus the building, if the system lacks an adequate vibration dampener - see VIBRATION DAMPENERS.
Voices in the ductwork? you bet. I still recall the discovery that a girlfriend's parents were monitoring our basement activity when suddenly, out of the air duct by our heads, came her dad's voice: Joanne! Time to come upstairs! HVAC ducts in buildings can transmit sounds between building areas, perhaps moreso when air is not moving through the ductwork. So watch out.
FAN & BLOWER Noises on heating and air conditioning systems may include ticking or clicking (fan blade hitting an obstruction), humming (motor troubles), rattling (loose fan pulley), squeaking (dry fan or fan motor bearings) and other sounds.
Humming sounds from HVAC systems are outlined below at COMPRESSOR CONDENSER NOISE and in that article at humming. [Aside: humming on oil fired heating equipment may be a normal sound transmitted to the building via oil piping attachment points. A/C refrigerant piping may also transmit equipment noises if it is not properly routed and mounted.]
Rattles at HVAC systems: look for loose hardware, loose fan blades, pulleys, or motor mounts; also possibly loose ductwork.
Other building noise sources: In case the noise you think is coming from an air conditioner or heats pump actually originates somewhere else, see NOISE / SOUND DIAGNOSIS & CURE
For heat pump system noises at the indoor air handler, also see NOISE CONTROL for HEATING SYSTEMS where we describe other heating system noise sources and cures.
How to Diagnose & Fix Noises Focused at the Compressor/Condenser & Condenser Fan Unit
If 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.
Banging or Clanking air conditioner / heat pump compressor noises, at least the costly ones, are usually due to a loose connecting rod, piston pin, crankshaft, or other internal part. Since compressors on most
modern commercial and residential air conditioning systems are a sealed unit, the only repair is to replace this (costly) part. A similar clanking or banging sound can be caused by loose internal mounts. Examples of banging, clanking, rattling noises from A/C and heat pump systems are found at our Questions & Answers section below.
Bubbling, hissing, refrigerant leaks: a catastrophic refrigerant leak on the air conditioner or heat pump high pressure side will make a loud hissing sound - but that sound won't continue for any longer than to dump the refrigerant into the atmosphere (something prohibited).
But a more subtle refrigerant leak that results in low refrigerant can result in refrigerant gas bubbles traveling around in the liquid refrigerant line. You might hear bubbling sounds at the refrigerant piping or see bubbles in the sight glass if your system has one. See REFRIGERANT LEAK DETECTION. Bubbling in the refrigerant is discussed at REFRIGERANT LEAK REPAIR.
Clicking, rumbling, ticking, rattling, clang and clunk at startup: loose hardware: Air conditioner compressor noise could be due simply to loose hardware such as a loose shipping bolt, tubing, or a broken spring. Does the
noise sound like a metallic rattle?
A visual inspection for loose hardware may help diagnose this condition.
Sometimes a shipping bolt may have been left in the unit and could be the source of a rattle. Loose refrigerant tubing or a bend in
tubing that carries it too close to the air conditioner frame or case can lead to rattling that is easily corrected with a careful
bend.
BEWARE of both
the chance of electrical shock and of injury from moving compressor
parts like the cooling fan which can easily chop off a finger. Homeowners should not attempt to open, disassemble, or repair an air conditioner compressor as
special training and safety procedures are needed to avoid injury.
Clicking noises from relays & controls can be heard at either the compressor/condenser or at the indoor air handler unit: A failing or defective thermostat or to a defective control itself can cause relays to click on and off repeatedly or the relay may ultimately buzz - see CONTACTOR RELAY DIAGNOSIS & REPAIR. Examples of clicking noises from A/C and heat pump systems are found at our Questions & Answers section below.
Hissing or Screaming A/C compressor, also described as "very loud screaming" by some sources [1], may be caused by excessive internal pressures - a dangerous condition. Watch out: turn off electrical power to the unit immediately.
Other more quiet hissing noises from the air conditioner compressor motor may (if the motor is a reciprocating compressor) be due to leaky internal valves.The compressor motor makes a hissing sound all during the time the compressor is running; when the motor stops the hissing dies down fairly quickly as the high side and low side pressures equalize. In this case the condition may not be dangerous, just an inefficient system that is costly to operate.
Examples of hissing noises from A/C and heat pump systems are found at our Questions & Answers section below.
Humming air conditioning compressor motors, fan motors, other electric motors, particularly if the motor is slow to start or does not start at all, may indicate that the starting capacitor needs replacement. See HARD STARTING COMPRESSOR MOTORS and see CAPACITORS for HARD STARTING MOTORS. If the compressor hums and never starts it could also be that the compressor motor has seized. In that case, leave the system turned off and ask for service from a professional.
Humming electric motors:
Note that while many electric motors make a modest and unchanging humming sound when running - a normal condition - any electric motor that is seized or having trouble starting may produce a humming sound at start-up, not just the A/C or heat pump compressor motor. For example fan motors at the compressor/condenser or in the air handler blower unit may hum when they cannot start. A failed motor, failed start/run capacitor, or low voltage are common causes of this humming. See ELECTRIC MOTOR DIAGNOSTIC GUIDE for help with motor diagnosis, and see CAPACITORS for HARD STARTING MOTORS.
Examples of more humming noises from A/C and heat pump systems are found at our Questions & Answers section below.
Humming, hard-start compressors, oil leaks: Another source of cooling system compressor noise is a low oil condition in the compressor unit. Low oil may be diagnosed perhaps by observing
evidence of compressor oil leakage on or around the unit. Modern residential air conditioning compressors are usually a hermetically sealed unit; it would be
abnormal to ever see oil loss around this equipment. (But don't mistake spilled oil from lubricating an electric motor or cooling fan
bearing for a refrigerant or compressor oil loss.)
Checking air conditioner oil level: A few residential air conditioning compressors and many commercial systems provide an oil
sight glass to permit a visual check of oil levels. On those units, when the compressor is running the oil level on the sight gauge should read 1/2 to 3/4 full.
If adding oil to a commercial unit, be careful not to add too much. Both too much or too little oil can cause compressor noises. On a residential compressor which is usually a hermetically-sealed motor, it is
not possible to see the oil level nor to add oil.
Squeals, normal A/C compressor: Normal air conditioner compressor squealing: Some compressors emit a high pitched noise during normal operation or just at startup. This noise should be brief and just at start-up, and will probably have always been present on the system if it's normal. Examples of squealing noises from A/C and heat pump systems are found at our Questions & Answers section below.
Start-up Compressor noises - refrigerant floodback: Air conditioning compressor noise could also be due to refrigerant liquid "floodback" into the compressor crankcase.
If this is the problem the noise will
appear only at the interval of compressor start-up. That's why it's useful for the inspector or service technician to be right at the compressor unit when the
air conditioning system is first turned-on. If this is the problem, a low cost repair might work: a crankcase heater can be installed to address this defect.
Ticking or loud clicking noises at the air conditioner or heat pump compressor unit fan: the fan blade may be contacting a bent fan screen or a stick or piece of debris that has fallen into the compressor unit; a loose or worn fan bearing permitting the fan blade to wobble might also cause this ticking or clicking fan noise.
Trumpet or trombone sounds from the compressor motor at shut-down, possibly loud, may be due to leaky internal valves; Meenen [1] asserts this is not a problem as long as a hissing sound is not observed.
Overheating, Blocked Coils, & Air Conditioner or Heat Pump Noise? we have had a field report from a reader who explained that a noisy outdoor compressor unit was, according to his HVAC service technician, traced to a blocked, clogged outdoor condensing coil. We speculate that perhaps the compressor was running hot and that correcting air flow across the condensing coil corrected that condition.
Cooling coils (indoors) or condensing coils (outdoors) can become so blocked that air flow is seriously reduced, possibly also leading to an evaporator or cooling coil icing problem indoors or an overheated, damaged compressor outdoors, or simply loss of cooling capacity of the system.
I have a National comfort Products CPO 2464-B unit which is an air conditioner and gas heating unit combined. The unit is about 5 years old. The air conditioner had become increasingly noisy. I called the party that installed the unit. After spending $90.00 for a service call I was informed the the external coils were dirty, opening up the unit light was not visible thru the coils.
I was advised to use a garden hose and rinse the coils. I did not have that available so I turned the unit on and using a watering can, poured warm soapy water onto the coils. this was done several times. the unit now seems to work properly. I did not see this particular problem described on your website. There may be other means of cleaning the coils but this was all I could think of. - C.A.P., Norristown PA
Questions & answers 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.
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.
A fan whacking something is a loose fan blade or broken fan shaft or bent screening around the fan or a stick or junk in the unit - any of which is a serious problem for the fan. If your service tech left the system like that s/he did not do such a hot job.
A unit that trips the circuit breaker is probably drawing high current - which, if the proper breaker has been installed, points to a problem with the wiring or more often the compressor motor on that circuit. A failing compressor motor draws high amps.
I'd also suggest checking out the voltage being provided to the system to be sure that there is not a low-voltage problem from your power source.
Follow-Up:
Thank you so much. Here's the problem. We just changed servicers, 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
Question: Buzzing Sounds at Air Conditioner or Heat Pump & Buzzing noises after A/C cooling coil change-out, Diagnosis, Repair
hi, i had problems with my central unit frezing 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 finaly 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:
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 conditioner
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 gaspack 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 conpressor noise since the unit was manufactured and installed before the AC season in 1994. Thanks for any suggestions you can offer. Doug
More info:
The unit is on the roof of a flat roof house and the noise is most noticable when standing below the unit. The noise is a higher frequency buzzing that could be a panel or other object vibrating close to the frequency of the compressor. To my knowledge, I have not been on the roof when the noise occured, or if it did, I didn't hear it with all the other noise. It seems to occur at various combinations of temperatures. Under some conditions, there is no noise, but other times, such as during a long run when we lower the temp after the sun sets, the noise may start several minutes into the cycle. A few times, I noticed noise soon after starting that only lasted for 20 seconds or so. We run the indoor temps between 85+ and 81 over a 24 hr period using a programmable thermostat.
I have banged and thumped on the case, removed the outdoor fan grill and looked for loose fasteners within the compressor/condenser portion of the case and checked all of the fasteners on the outside of the case to make sure they were tight. I put card-stock shims between joints of panels, etc to prevent any vibration that might occur. So far, nothing has eliminated the noise that seems to occur only under certain conbinations of outdoor/indoor conditions. 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 noticably different, but the noise pattern may have changed somewhat, while the sound is about the same, when it does occur.
Last winter I removed the top of the unit to oil the indoor fan motor. That is the first time it has been removed since we owned the house. As far as I know, everything was reassembled correctly. My experience is limited to light to medium maintenance of only my own auto/home AC systems for the past 4 decades. I installed a quick start system about 5 years ago on general principals because one worked wonders on similar but smaller gaspack in another part of the house. - Doug
Reply: Buzzing Sounds at an A/C or Heat Pump System May Mean Failing Electrical Parts
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.
Noise diagnosis is tricky in part because there is some subjectivity in how people describe sounds (buzzing vs humming for example). Taking care to not get whacked by a moving part like a compressor fan, one can sometimes use a mechanic's stethoscope to get right to the source of a sound from mechanical equipment.
Followup:
Dan,
Thanks for your suggestions. I'm relieved that you didn't point to the compressor as a typical source for noise like mine, but I know I can't rule it out yet. I took a dowel rod up to listen to for any noises, but at 94 deg, it didn't make any abnormal sounds (my wife confirms). I did notice that the top of the condensor at one edge was vibrating and a potential source of noise. I'll check it later. I opened the control compartment and all seemed normal and no loose components there. I would like to be able to listen to the compressor, but there's no way without dueling with the outdoor fan and I would likely lose. I'll let you know if I ever come to any conclusions.
Followup:
Dan,
A while ago, I wrote about intermittent noise from my roof mounted gas pack. After spending a lot of time on the roof and poking around inside the compressor compartment, I am reasonably certain the noise is coming from the compressor itself. I checked the compressor mounts and they are solid and there are no loose parts to vibrate and cause noise. In the process of pushing the compressor around to see if the mounts were loose, I heard the compressor hit the side of the shell.
I was looking around another site and the owner mentioned that the compressor suspention 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.
Hopefully I will replace it before there is a burnout. Would you recommend installing a filter/dryer even if there is no hard failure? I don't believe Trane installs them in new-build units and there is certainly none in the compressor bay. If the compressor banging against the shell is releasing particles into the system, is there a spomething other than a dryer that will catch the particles?
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:
re: noise is coming from the compressor itself - a failing compressor motor indeed can become noisy;
I would not install a filter/dryer before replacing the compressor because
- an extra cycle of opening the refrigerant piping system risks contamination and also done properly requires vacuuming and cleaning the whole system - it's a bit of a costly procedure to do at that point
- when the compressor is replaced a filter/dryer would normally be installed as part of the job
But if you wait for a failing compressor to burn up the result can be extra contamination in the refrigeration system.
For those reasons I'd ask for an experienced HVAC tech to look at the system, diagnose the problem, and then I'd decide if it were time and better to replace the unit now, or shut the system down and replace it before start of next season.
Follow-Up:
Dan,
Thanks for the tips. All makes sense to me. I will consult with the a dealer that I know, before I do anything. I am inclined to just replace the compressor though, if I can find one at a reasonable cost. I found a new AM Std compressor on eBay that appears to be interchangable with the one in my unit, but so far, I can't find cross reference data that I trust. I will probably use it lightly until we get into cooler weather (6 wks)and hope for the best, but prepared to replace the whole unit if crashes. I'll add a filter/dryer if I replace the compressor. Sorry if I didn't make it clear, I wasn't thinking of a two step operation.
I found a video on youtube 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.
Thanks again for the help. - Doug
Dan,
Regarding installation of a filter/dryer; the filters I have seen on HVAC parts sites are for installation on the suction side. When I installed an AC in my house in '88, I installed a filter/dryer in the liquid line, near the coil as recommended at the time. It seems to me that it makes more sense to filter the liquid entering the TXV than to filter the gas entering the compressor. What am I missing? I purchased the compressor on eBay. It turns out that it was exactly the P/N specified in the parts list for the equipment. The gaspack contained what I assume was an earlier equivalent part. - Doug
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 & manully started fan turning.
Fan started running on its on, but at a very low speed, nothing like it normally does. Any suggestions? Inside unit seems to work normally. - Hill
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 Compressor
The 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 clancking 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 Pump
Mom: 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:
A fan that is wobbling and missing a blade is dangerous, likely to damage the equipment. I'd have shut it off immediately. If the fan problem was local to the blade assembly itself it may be a reasonable repair; if the fan spins off of its shaft and cuts and smashes other components inside the compressor/condenser (assuming we are talking about the outside unit) or inside the air handler/blower assembly (the inside unit) then other damage will need to be examined and repaired. Could be costly if electrical components were damaged or a refrigerant line was cut.
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 seconds
Hi. 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" approx every twenty seconds or so, as if the unit is trying to turn on.
What is wrong ? - Hilary
a/c condenser unit sounds like a popcorn machine only when going off - Troubled
Reply:
Ron:
SPECULATING: if the A/C is not stopping it could be that your thermostat is continually calling for lower temperature than the system can reach, thermostat wires are shorted together, a control board is damaged, or something else that this guessing has not anticipated. Try turning off all power for an hour.
Hilary: if your condenser fan won't run you need a service call. The tech may find a bad start/run capacitor or fan motor, or on occasion a bad control board or switch.
Adam: I'd call a service tech; it sounds as if a relay is not working properly; but first just take a look to see that your fan blade is not wobbling as it slows down; sometimes a loose fan blade can contact something inside the condenser.
Question: Hissing Sounds from the Heat Pump or A/C System, Diagnose, Repair
Hissing 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 conditioner
sir i check my out door unit i see the compressor is geting cold and after few muenits the ampers will going up start in 17 up to 20amp.,and it comes sound like noise, yes that was my compressor also, din after few meunits suck line cames ice and noise coming like ssssssssssssssssssssssssssssssssssssssssss..... - Danny Carumba
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.
Darny: Because SOME A/C compressor hissing noises can be due to dangerous internal over-pressure conditions, I'd ask a service technician to check the air conditioner promptly.
Question: Hissing in "surround sound" after installing a new high efficiency A/C and Heating System
I 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 system
El, before installling 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.
Hi Dan...thank you for responding to my question....I cannot track down the source...it's Surround sound....everywhere....not eminating 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 noone 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 elses' 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, alot of underground cables under our particular front yard:PSNH, cable...etc. it would cost alot...I know it would cost alot, 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:webpg, 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 NHPUtilities (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: Groaning, Huffing, Compressor making Wuw, Wuw, Wuw or wa-wa-wa sounds or Huffing & Puffing Sounds: examples, diagnosis, repair advice
Question: 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
Reply: Huffing Puffing A/C Units
Herbert: 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/
Reply: Hard Starting A/C and Heat Pump Compressors May Make Groans, Wuw, and WaWa or Wah-Wah-Wah- Sounds
Tiny, 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 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 System
I 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.
Would appreciate any suggestions.
Thanks -
VikI
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
Reply: Pinning down the exact noise source on HVAC equipment
A 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.
Often pipes transmit vibration into a building chiefly because they are attached to building walls, ceilings or floors that in turn act as a giant speaker cone. If the piping is rubber mounted or cushioned with foam you can often eliminate the noise indoors. (Of course you may still need an equipment repair.)
Question: A/C or Heat Pump Compressor Rattling & Vibration Noises
Question: 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 mins later we turned the AC back on and it took about 10 mins 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 mins 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 Darnit. 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: Regular cycles of A/C noises every 30 seconds, Vibration Sounds
AC 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 compressors
Rebecca: there are several failures that can cause a frequent cycling noise in HVAC compressors such as
- a start/capacitor that is not working or not able to start the motor - the motor may attempt to restart repeatedly until a hard failure occurs
- a thermostatic expansion valve that is improperly adjusted or stuck open can cause a hunting or seeking cycle in which refrigerant is not only improperly metered, but liquid refrigerant can enter and destroy the compressor
I tend not to suspect a thermal overload because usually when electric motors overheat and trip off on thermal overload it takes much longer than 30 seconds for the control to automatically reset. Reply: Rattling, followed by Low Humming Noises and hard starting compressorsKim: 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 chanaged. Is it ture? 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 noises
Sounds 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 Compressors
our compressor started squealing intermittantly 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 compressorsSecn: ... "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.
BUT ... as we cited in the article above "Normal air conditioner compressor squealing: Some compressors emit a high pitched noise during normal operation or just at startup. This noise should be brief and just at start-up, and will probably have always been present on the system if it's normal."
In your case it the compressor never squealed before and is noisy now, it's less likely to be "normal" and more likely to mean the unit is nearing end of life. Your choices may be to install a hard-start capacitor to try to keep it going as long as possible, figuring soon it'll need replacement, or to go ahead and replace it now to reduce the risk of being days without A/C during hot weather.
I'd be inclined to limp along until the end of cooling season if possible - the A/C techs will be less busy then.
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. hahaha. 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 cuz 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
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Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Thanks to reader Michael Anderson, 8 May 2009, for discussing clicking sounds coming from air conditioning equipment.
Thanks to Diaz, Domingo I. CIV NAVAIR Bldg.2118, rm. 131: domingo.diaz@navy.mil
- Ming Diaz, Great Falls, MD for editing help with the text about discharging air conditioning compressor capacitors - 3/07 DF]
Thanks to reader Charles A. Plinton, Norristown, PA, for discussing A/C compressor noise, coil cleaning, and system maintenance - August 2010
[1] Scott Meenen, G&S Mechanical Services, email: jsmeenen@toad.net; web search 5/1/11 http://toad.net/~jsmeenen/compressor.html
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend)
Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
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