Diagnose these HVAC noises:

Screaming, singing, squealing, trumpeting, water gurgling, whining, whistling, wuwuwu sounds at an air conditioner or heat pump.

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.

HVAC Noise Diagnosis of screaming, singing, squealing, trumpet, water gurgling, whine, whistling, wuwuwu sounds

Article Contents

• SCREAMING or whistling or shrieking A/C compressor/condenser unit sounds - warning about high pitched sound from the compressor/condenser unit !
• SILENCE no sound whatever coming from HVAC equipment?
• SINGING, rumbling, whining A/C compressor/condenser or blower fan motor noise
• SQUEALING air conditioner and heat pump equipment, diagnosis
• TICKING NOISE DIAGNOSIS
• TRUMPETING noises from compressor motors on A/C and heat pump systems
• WaWa, Wow wow sounds from A/C or heat pump system, diagnosis
• WATER SOUNDS in HVAC refrigerant piping or coils
• WHINING A/C compressor/condenser or blower fan motor noise
• WHOOSHING SOUNDS from the expansion valve
• WHISTLING sounds at HVAC air handler or ductwork
• WU WU WU sounds from A/C or heat pump system, diagnosis

 

Screaming HVAC compressor/condenser unit noise & warnings

Watch out: : turn off electrical power to the screaming A/C Condenser / Compressor unit immediately. It may be unsafe to continue to operate.

Common causes of loud screaming sounds at an air conditioner or heat pump compressor/condenser unit

• Dangerously high refrigerant pressures: 
  
  A Hissing or Screaming A/C compressor, also described as "very loud screaming" by some sources [1], may be caused by excessive internal refrigerant pressures - a dangerous condition.
  
  Compressors include a high pressure sensor that should shut the system down if internal pressures are approaching a dangerous level.
  
  But if the compressor continues to run and is screaming, turn it off immediately as the system is unsafe.
  
  Possible actual causes of high pitched noises at the AC Compressor/condenser unit also include other sources in this list.
  
  
• Internal compressor leaks:
  
  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.
• Noisy AC / Heat Pump Compressor Valve sticking or Jamming:
  
  According to some reports, a failing valve inside of the compressor motor itself [citation needed] that is whistling or shrieking at the end of a compressor on-cycle, as refrigerant pressures equalize back in the compressor motor itself. - thanks to reader Bryce Dodds for posting this comment
  
  at AC HIGH PITCHED SOUND our YouTube video of compressor noises - 2017-01-18
• Failed or damaged valves
  
  in the compressor motor OR damaged TEV Thermostatic Expansion Valve, noise caused by refrigerant bypassing the valves attempting to equalize pressure in the system.
  
  A sticking or failing thermostatic expansion valve may scream (TEV or TXV) - if it is not opening when it should, giving excessive pressure on the high side of the AC system
  
  Damaged compressor or TEV valves may in turn have been caused by a liquid refrigerant floodback into the compressor motor, in turn caused by an overcharge or a TEV malfunction.
  
  Damaged TEV may be due to dirt contamination, mis-adjustment, or icing.
  
  
• Failing bearing at an electric motor such as a fan motor or even come compressor motors can cause a loud screaming or screeching sound.

Loud screaming noises at the compressor unit may also be described as a high pitched compressor noise, compressor whining, compressor screaming, or bearing noise.

Since some people describe these sounds as hissing rather than screaming, also see HISSING SOUNDS, HVAC

Other Sources of Screaming (high pitched whine or whistle) Sounds from HVAC Equipment

• Failing motor bearings such as in an electric motor; check the compressor/condenser unit fan motor and motor bearings for bearing failure or fan motor shaft binding.
• Failed mechanical shaft bearings such as on a squirrel cage blower fan
• Noisy themostatic expansion valves or TEVs may also whistle - typically an indication of debris clogging in the device
• Also see SQUEALING air conditioner and heat pump equipment, diagnosis

With power off check for play in the blower fan assembly. Sometimes we temporarily confirm a bad bearing by putting a drop of oil right into the bearing assembly. If the noise stops we've identified the parts that need replacement.

Examples of field reports of hissing noises from A/C and heat pump systems are found at our FAQs section below.

Silence: No Noise, Silent or Soundless HVAC Compressor or Fan Unit

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".

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.

Squealing A/C or Heat Pump Compressors: examples, diagnosis, repair

Loud squealing, clanking compressor noise

Here we provide a video of noisy SQUEALING CLANKING AC COMPRESSOR - condenser unit - 6 Sept 2013

This brief video contributed by one of our readers (L.M.) demonstrates start-up troubles and loud continuous squealing, clanking, and what I take to be some humming at the outdoor fan-compressor unit. The unit is unable to start and run normally.

Sources of squealing noises at an air conditioner or heat pump compressor

• Check for a loose pulley or belt on belt-driven fans in the air handler or at the compressor/condenser unit (belt and pulley driven components are not always present)
• Listen for a failing bearing in an electric motor; look for lubricant leaks around a motor shaft; check for motor overheating due to binding bearings; look for loose wobbly drive shaft coming out of the motor end bearing;
  
  In the air handler, with power off for safety, check for a loose or wobbly blower fan or squirrel cage fan shaft bearing
  
  At the compressor unit check for a bad fan motor bearing
• Expansion valve failure: Check for an icing or dirty or sticking thermostatic expansion valve or TEV
  
• Check for a failing compressor motor:
  
  SCREAMING A/C compressor/condenser unit sounds - shut off the system and see this warning!

Discussion of possible causes of Squealing Compressor/Condenser Unit

Check for a fan blade assembly that is hitting an obstruction, is loose on its drive shaft, wobbling, hitting the enclosure.

If the noise is intermittent, that argues against a loose part or assembly such as a fan problem.

Squealing noises may come from a unit that is unable to start - a bad starting capacitor, compressor motor or bearing.

Cyclic sort of clanging-buzzing sound may be a motor or fan motor trying to start in response to a start relay;

Continuous squealing though sounds like a bad motor.

If the squealing noise varies by outdoor temperature or weather, we speculate that during the day the compressor is running continuously in hot weather, perhaps also making the motor itself quite hot.

Then finally in the evening as temperatures fall, the compressor and centeral A/C gets ahead of the building cooling load enough to cycle off - but not for long. Trying then to re-start fairly quickly the motor may be unable to re-start against a remaining high refrigerant head-pressure.

Such troubles can be caused by a failing compressor motor, an improper refrigerant charge (less likely), a sticking refrigerant control valve (possible), or something else I haven't thought of.

It's time for a service call by an experienced HVAC tech.

Also see RUMBLING NOISES A/C compressor/condenser or blower fan motor noise

Also see the article beginning at the top of this page for some discussion about A/C noises and

HARD STARTING COMPRESSOR MOTORS

Whoosing Sounds at HVAC Equipment: causes of periodic whoosing noises on heat pump systems

• Whooshing sound in refrigeration piping when the compressor stops, usually at the expansion valve, at the end of a compressor on-cycle is normal and should abate after less than a minute. You're hearing refrigeration pressures equalizing in the air conditioning or heat pump system when the compressor is no longer sending out high-pressure refrigerant.
  
  Refrigeration pressure will seek to equalize in the high-side and low-sides of the system.
  
  If on the other hand you also hear bubbling, gurgling or rattling sounds inside the refrigeration piping that may not be a normal condition and may indicate low refrigerant charge.
  
  See GURGLING SOUNDS from the AC or refrigerant piping.
• A brief whoosh noise may be heard at or near the reversing valve on a heat pump during cold weather operation. If it lasts just a few seconds, this noise is normal. You are hearing refrigerant moving through the valve in a reversed direction as the heat pump is temporarily suspending heating operation to go into defrost mode.
  
  This step prevents the heat pump and the outdoor coil from becoming blocked by ice.
  
  Special thanks to Hannaberry HVAC, an eastern Pennsylvania air conditioning and heating contracttor for their cogent description of this whooshing HVACR noise with which we were not familiar.
  
  Hannaberry notes that until the refrigeration pressure has equalized in the system (just seconds again) the compressor motor may also sound louder and perhaps "tinny".
  • Hannaberry HVAC, "Outdoor unit makes strange or loud noises", Hannaberry HVAC, 200 Schantz Road, Allentown, PA 18104 Phone: 610-366-9400, USA, Website: http://www.hannabery.com Telephone: 1-800-544-4328,
    
    locations in Allentown, Quakertown, and Clarks Summing, Pennsylvania, USA, original source: http://www.hannabery.com/faq8.shtml

Whistling Noise at HVAC Equipment: diagnose whistling at the air handler or compressor/condenser or in Ductwork

Whistling sounds in HVAC duct work or air handlers are often due to air leaks see

• SUPPLY DUCT AIR LEAKS
• RETURN DUCT AIR LEAKS
• Also see our more general article on AIR LEAK NOISES in our article on house noise diagnosis

Whistling Thermostatic Expansion Valves (TEVs)

On refrigeration systems that include a liquid refrigerant receiver and as long as there is adequate level of refrigerant in the system and the TEV is working, the refrigerant charge amount is not absolutely critical.

But on any refrigeration system, receiver or no, if the refrigerant charge gets too low (there is a refrigerant leak somewhere) then refrigerant gas cycles up through the TEV rather than liquid refrigerant.

The result is that the TEV will begin to run "wide open" and it will often make a loud whistling sound.

A whistling TEV means low refrigerant. (You won't hear whistling at a capillary tube metering device).

Listen for a whistling thermostatic expansion valve - a sign of low refrigerant and if you hear that whistling sound

see THERMOSTATIC EXPANSION VALVE TEV INSTALL, DIAGNOSE, REPAIR

Reader Question: Whistling squealing window air conditioner [recording provided]

I have a window/wall air conditioner that recently started making this very annoying "squealing" sound. It doesn't happen all the time though... In fact, it almost seems to trigger when something else happens (e.g. when the walls rattle or vibrate, or when a door closes, etc) although sometimes it just kind of happens.

The unit is actually mounted in the wall on a chassis and when the noise is active, it's pretty loud inside the house but it's almost non-existent if you're standing outside next to the compressor. The only way I can get it to stop squealing is to smack it on the side a few times, but even with that it still starts to squeal again (at one point or another).

WHISTLING WINDOW AIR CONDITIONER is a recording I made of the sound in case that helps.

Any help / advice is most appreciated. Also, because I rent the place I'm kind of at the mercy of the landlord (which is why I haven't just replaced it myself).
Thanks! Jeremy 8/28/2014

Reply:

Jeremy a window AC compressor motor that's squealing - if the sound is indeed coming from the motor - would most likely have the same causes as the squealing noises in the article above.

"Typically a squeal means hard-starting which could be a bad compressor motor, bad start capacitor, or a compressor having trouble starting against a head pressure (try leaving the system off for 30 minutes and then re-starting)."

On some air conditioners the noise you describe could on occasion also be traced on occasion to a bad thermostatic expansion valve. The fact that the noise stops when you smack the unit could point in that direction.

I'll post your recording HERE [link to .m4a noise recording] to encourage other hvac techs to comment further.

Reader followup

Thanks for the response, mod.

A little update. I made a video to try and give you a little better idea of what's going on, because I believe the squeal is coming from the air handler/blower fan.

Also, while my camera was inside the top of the unit I noticed a buildup of water at the bottom and then realized that normally the unit drips water on the outside but I haven't seen water dripping in quite a while (about a month).

Assuming the squeal is coming from rust on the shaft between the blower and the partition, and that the rust is coming from the water that would normally drip onto the ground, is there anything I can do to fix it? Or even make it so it drains the water again? I have a feeling that even if I'm somehow able to fix it, the standing water will just cause it rust over again (assuming that's the problem, of course).

Video can be seen here: jeremy [dot] ws/ac [dot] php

Jeremy's shrill high pitched SCREAMING WINDOW AIR CONDITIONER RECORDING recorded from his video [3.6MB sound file]

Reply:

I think you're right, Jeremy - in that I see the blower cage assembly is wobbling like mad. Perhaps there's a failed bearing in the squirrel cage fan. Turn off the system, remove power, and see if you can wobble the fan assembly on its shaft.

I added links to a sound recording from your system, and if you can email me the video or provide a download link I could add it here for other expert HVAC folks to comment upon.

Causes of Whistling Sounds at the AC Air Handler / Blower Unit

Two days ago, when my AC turned on, it had a strange whistling/ raspy noise. I have taped the noise but not sure how I can upload it to share with you.

I had a pretty dirty filter that I changed, but the noise has not abated at all. When we opened up the system, the fan motor appears to be working normally.

I did confirm this morning that fan only makes same noise as AC, so its the fan not the AC that's causing the ruckus.

Any help you can provide would be most welcome. I am currently out of work, so really need to know if this is dangerous/ could make the matter worse by using or just annoying. Thank you! On 2015-09-02 by Dara

Reply by (mod) -

Dara:

Usually whistling is air movement through or over a duct leak, less often over an obstruction in the ducts.

A change in air velocity can make noises show up, such as when there is a dirty air filter or when the filter has been left off or when a blower unit door has been left open.

...

Wow Wow WaWa or WuW sounds from an A/C or heat pump system

Please also see GROANING, HUFFING, WUWUWUsounds from A/C or heat pump system, diagnosis where we discuss these noise descriptions together.

Question:

(June 11, 2015) Odd wahwahwah noise said:

I am a new condo owner. The other day I turned on my AC and left it on auto. It worked fine, no unusual noises. Then last night I decided to turn off the AC and open up the windows. My AC unit is located outside in a cabinet on the porch. My bedroom is upstairs.

While I was laying in bed trying to get to sleep I heard a very loud wahwahwah noise,I knew my AC was off but it sounded like a fan or compressor on.

I went to see if air was coming out of the vents and it wasnt. I confirmed both of the thermostats were turned off. I could hear the wahwahwah throughout the house.

After 15 minutes it stopped. then it started up 5 minutes later.[Wah Wah Wah noise from the A/C unit] this cycle continued and continued and i was baffled and agitated. Finally, i decided to go turn on my ac, so i did. I let the air blow through the vents for a minute or so then turned it off. the sound NEVER came back.

I dont know what this could be since the unti was OFF, but after i started it up again and then turned it back off it appeared to resolve the issue. Now I'm worried to even turn the AC on again. I do have a home warranty and its only a $60 service call to have someone come out, but has anyone heard of this issue?

Reply:

Sure Odd. In the HVAC noise links above

see NOISES, HVAC SYSTEM DIAGNOSIS - home and you'll see several categories of noise descriptions

including GROANING, HUFFING, WUWUWU the one you name.

Question: whistling AC at time of turn off

My a/c unit is making a high pitched whistling noise when the unit goes off. Any ideas? (May 19, 2014) Anonymous

Reply:

Anon,

at inspectapedia.com/noise_diagnosis/HVAC_Noise_Diagnosis.php

we discuss whistling that is often traced to air leaks in the duct system. Let me know if that's your case.

...

...

Continue reading at NOISES, HVAC SOUND RECORDINGS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see HVAC NOISE-5 SCREAM SING TRUUWU FAQs - questions and answers posted originally on this page

Or see these

HVAC Noise Diagnosis Articles

• NOISES, HVAC SYSTEM DIAGNOSIS - home
• NOISES, HVAC SOUND DESCRIPTIONS - Index to all noiseMPET WHINE Ws & sounds
• HVAC NOISE-1 BANG BUZZ VIBRATE - banging, bearings, buzzing, thumping
• HVAC NOISE-2 CHATTER CHIRP CLANK FAN GRIND GROAN - chatter, chirp, clank, clunk, cyclical, fan, fog horn, honk, moan, grinding, groan, growl
• HVAC NOISE-3 HISS HOWL HUFF HUM - hiss, howl, huff, hum, groan, woo wuu wuff or humming noises
• HVAC NOISE-4 POP, RATTLE, ROAR, RUMBLE - loud start, popping, rattling, roaring, rumbling, running water
• HVAC NOISE-5 SCREAM SING TICKING TRUMPET WHINE WUWU - high pitched noise, tick, scream, sing, squeal, trumpet, water sounds, whine, wuwuwu

Suggested citation for this web page

HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE I NDEX to BUILDING NOISE DIAGNOSIS

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