Air conditioner or heat pump noise diagnosis & cure Q&A set #3:

More FAQs about the causes & cures for heater, air conditioner, heat pump, or other refrigeration system noises to help tell us what repair is needed.

This air conditioning repair article series discusses the diagnosis and repair of cooling or heating system noises and sounds of all sorts.

A/C & Heat Pump System Noise Diagnosis & Repair Noise FAQs

These questions on finding and curing noises traced to heating, ventilation, or air conditioning systems were posted originally

at NOISES, HVAC SOUND DESCRIPTIONS - be sure to review the diagnostic advice at that article.

On 2018-11-05 by Vickie - A/C doesn't work on hot days

This summer AC would not coolin very hot days. On the heat, when unit starts it runs for 5-10 seconds and then stops

On 2018-11-05 by (mod) - my heat pump short cycles on and off when in heating mode

Vickie

I am sorry that I can't offer a specific diagnosis but frankly we just have too little information to say anything useful beyond the compressor failure articles listed right at the end of the article above.

I would call an HVAC service technician for on-site diagnosis and repair help.

But before doing that, also take a look at our description of the common causes of air conditioner or heat pump "short-cycling" on and off, found at

SHORT CYCLING AC COMPRESSOR inspectapedia.com/aircond/Air_Conditioner_Short_Cycling.php

On 2018-10-16 by Alex wooing sound coming from new rheem AC 14 seer non variable speed.

What is cause of wooing sound coming from new rheem AC 14 seer non variable speed.

On 2018-10-18 by (mod) - wooing sound of air conditioners

Gee, Alex, I honestly don't know. Could you describe "wooing sound" a bit more. Surely the AC isn't making affectionate noises.

See HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU - scream, sing, squeal, trumpet, water sounds, whine, whoosh, whistle, wuwuwu, or silence

for more detailed diagnostic advice.

On 2018-09-23 by BJ - Squealing coming from our new A/C unit

I had a new unit installed in April. Still cool here that time of year so we were using heat. When it warmed up and we turned the ac on, we started hearing a loud pitch squeal. It only happens late at night/early morning. Typically between 1 and 6 am. It happens in between cycles.

Not directly before or after startup. It comes from the component that's in my crawl space (I'm not too sure what it's called).

I've tried different things to try to get it to stop and have figured out that it only squeals when the thermostat is set higher than the outside temp or close to the outside temp. In other words I have to have it set much colder than the temp drops at night.

For example, I have it set to 68 starting at 9pm.

Last night the temps dropped to 67. Woke up to it squealing this morning.

The installer cannot figure out what it is. He replaced the brand new blower motor thinking that's what it was. Didn't help at all. Any ideas? It's about to drive us crazy!

Reply by (mod) -

if your technician has ruled out all mechanical noise sources such as those that might be related to a blower fan or it's driving Parts, another thing to check would be the thermostatic expansion valve

2-minute humming sounds from our HVAC system at 1AM

Randomly, around 1AM there is a humming sound that starts out low and ends high (lasts about 1-2 minutes). It is not reproducible, the HVAC guy replaced the filter on the first trip, blower motor on the second but it continues. I recorded it this morning at 120AM, it sounded strongest around the whole house humidifier area.

@Jeff R, Also, turning the furnace off at the thermostat does not make the noise stop, nor switching form cold to heat.. On 2018-08-21 by Jeff R

Reply by (mod) - Diagnose the humming sounds by following the clue frrom your HVAC guy:

Jeff

Diagnose the humming sounds by following the clue frrom your HVAC guy:

Look at what electrical equipment might be running or trying to run.

A motor that is having trouble will often hum - before it burns-up or fails.

Search InspectApedia.com for ELECTRIC MOTOR DIAGNOSIS or for HARD START CAPACITOR to understand more about that possibility.

Of course replacing an air filter won't mean much to a failing blower motor, but maybe the tech figured as long as she'd gone to the trouble to look at the system she might as well do something useful.

See HVAC NOISE-3 HISS HOWL HUFF HUM - hiss, howl, huff, hum, groan, woo wuu wuff or humming noises

On 2018-08-12 by Ryan S - Rushing water sound from floor vents

My townhouse has floor vents, the first few vents closest to the A/C Unit have a very loud rushing water sound coming from them. Like loud enough that it sounds like a rushing stream lies beneath my floors.

Our largest unit, is a 50 pint and it produces anywhere from 150-250 pints of water per day.

I'm still training in Home Inspection and i'm stumped on the water running sound. My landlord isn't very quick to respond to problems here, so that further complicates things.
Any suggestions on the running stream noise?

On 2018-08-14 by (mod) -

check and tell me if they're running water sound is associated with refrigerant piping

On 2018-08-14 by Ryan S

No sir, I opened the HVAC closet and no noise like that coming from refrigerant piping. Another thing I just noticed, when you open the HVAC closet, you get a rush of freezing air coming out, like that closet is super freezing. And the air coming out of the vents isn't near as cold.

On 2018-08-14 by (mod) - Flowing air doesn't sound like running water

I'm baffled myself Ryan. Flowing air doesn't usually sound like running water - perhaps there is something loose in the ductwork.

Or you could be hearing condensate running down a disposal drain.

On 2018-08-09 by Allie

My AC unit indoor will run for awhile then start making this banging noise even though it’s not cooled to desire temp yet. It’s like it shuts off and is trying to start back up. Unit is only 2 years old. Help!

On 2018-08-10 by (mod) - air conditioner banging noises

Allie

Let's start with the diagnostic suggestions for air conditioner banging noises at

• BANGING A/C or heat pump
• BANGING NOISE at AIR HANDLERS or in DUCT SYSTEMS

On 2018-04-24 by Ruth Knocking sound from Trane air condidtioner

Trane AC is a little over a yr old and makes a knocking noise after it shuts off.

On 2018-04-24 by (mod) -

Ruth

I'm a little concerned with the noise you're describing could be due to liquid slugging which can damage the compressor. I would prefer to turn the system off and call your service company for an inspection and repair.

Let me know what you're told and I may be able to suggest follow-up comments or questions.

On 2018-03-11 by Pap

Outside unit hums on start up about 2 seconds and then runs normal.

On 2018-03-11 by (mod) - Outside unit hums on start

Sounds like a hard-starting compressor.

On 2017-12-12 by Bryan W.

My indoor A/C handler is making a loud buzzing noise when the heat is turned on, the noise starts as soon as the heat kicks on and ends when the heat kicks off.

I'm pretty sure my system has a heat strip if that helps. What should I be looking for if I remove the front plate of the handler to take a look inside?

On 2017-12-13 by (mod) - buzzing noise repair

Bryan,

Please take a look at the description of a common sources of buzzing noises given near the top of NOISES, HVAC SOUND DESCRIPTIONS. That would be the best place to start

On 2017-12-10 by John

The outside blower unit makes a loud Noise when it shuts off. Almost sounds like a bad bearing. It occurs more frequently in the colder early morning hours. What needs to be done to correct it?

On 2017-12-10 by (mod) - banging noise repair

John

Start with the Banging Noise diagnosis descriptions found at

https://inspectapedia.com/noise_diagnosis/HVAC_Noise_Descriptions.php#Bang

Loud whistle noise at the compressor side it starts

Hello guys!
I got a 4ton unit that is making a whistle noise at the compressor side it starts after like 10min from starting the ststem but it doesn't shut the ststem off, it sounds like the safety valve on any compresor

i can hear a small whistle, if i shut off the system and wait a minute or 2 i turn it on and it goes away for another few minutes!

My question is if this is a sign of a problem or its normal? If this is a problem what can i look for? Thanks in advance for any help given On 2017-05-21 by Angel

Reply by (mod) -

Angel

Whistling is often a problem at an expansion valve or sometimes a more serious overpressure problem at the compressor.

We discuss the common causes (and cures) for whistling noises at an A/C compressor in HVAC Noise Group 5 at https://inspectapedia.com/noise_diagnosis/HVAC_Noise_Descriptions_5.php please take a look and then don't hesitate to ask for more help.

Danile

On 2017-05-15 by Ralph S

I'm at my wits end over this.... I moved into a 20 year old condo two years ago.

I'm on the third floor of a four story building. Intermittently, I hear a clanking noise that sounds like someone throwing a tennis ball against a cement wall.

I hear the noise throughout my entire apartment because the noise is coming out of my A/C vents. I even hear the noise if all my power is turned off.

On 2017-05-15 by (mod) re: clanks, clunks, noises like tennis ball tossed against a wall

Ralph:
You've done one of the good steps in tracking down the source of an annoying noise by turning things off. Here are some more considerations:

A neighbor's mechanical system or equipment could be running, so more turn-off diagnosis could help

Metal ductwork often makes noises like those you describe as the ducts expand or cool: sheet metal clunks and thumps. Those sounds are usually most noticeable near the start or after the end of an HVAC system turning on or off or its blower fan turning on or off.

If you have not done so be sure to read
CLANKS CLUNKS from air conditioner or heat pump system - found at inspectapedia.com/noise_diagnosis/HVAC_Noise_Descriptions_2.php#Clank

Track down the noise to its source by careful listening, with helpers, in various locations to see where sound is loudest.

Try using our NOISE LOG (search InspectApedia using the search box above) to relate noises to weather, temperature, time of day, etc.

 

On 2017-05-12 by Cindy

*live in Florida

A.C. Unit making loud squealing noise. So I shut it down. Love in Florida on fixed income .

On 2017-05-15 by (mod) re: where to go to find squealing noise sources in HVAC systems

Cindy, squealing noises at the A.C. unit have several causes and vary in importance. Details are at

inspectapedia.com/noise_diagnosis/HVAC_Noise_Descriptions_5.php

 

Builder says fan noise is caused by "wind gusts" getting in the vents

Moved into new construction 3 floor SW facing condo and have an intermittent, "fan like" noise which is unpredictable , lasts precisely 12 minutes, is not related to fans being on or off, is located in the ceiling area of the dining room on north side of condo and is heard in next door condo .

Builder says it is caused by "wind gusts" getting in the vents and there is nothing he can do about it. He has never heard the sound. The noise does not necessarily occur when it is very windy , when it is colder and is not heard when the fans are turned on in the condo. What is this? On 2017-02-24 by Anonymous

Reply by (mod) re: wind gusts as sources of regular-interval building noises

Anon

I would look again at mechanical systems. It's just not reasonable that wind gusts would occur at regular intervals and be of regular lengths.

 

 

On 2016-08-12 by Anonymous

I have a Fujitsu split unit in my garage. Recently it has started making a rattling noise on the wall unit. It will go away while I touch it on the side (actually on a piece of plastic) but when I let go, it makes the same noise. It will eventually go away for a while but then happen again. I don't see anything loose on it. Please help.

Reply by (mod) re: popping, rattling, roaring, rumbling, running water sounds from air conditioners

Anon in the live links near the top of NOISES, HVAC SOUND DESCRIPTIONS you might enjoy reading

HVAC NOISE Group 4 - loud start, popping, rattling, roaring, rumbling, running water

where we discuss causes and cures of rattling noises.

What you describe might just be a loose part, or on the other hand, a motor that's vibrating (and on the way out) could be shaking the outdoor unit.

 

On 2016-07-07 by Mary Hale Buzzing rooftop condenser unit in Florida

Above my condo are 3 large condensers that service a restaurant on the ground floor of the building. I can hear 2 of them come on and off

. One has a nearly continuous buzz / hummm sound, the other one has more of a motor sound, almost like a small plane that wants to take off. This is summer in Florida, so they are on virtually all of the time.

Builder tells me that due to hurricane code they must be mounted directly on the roof. *they are over my bed room! Is there any help for this? thank you ~ Mary

Reply by (mod)

Mary,
Start with your local building department about location requirements.

Even direct rooftop mounting does not prohibit sound isolation methods.

Also from your description the equipment may not be working properly and may fail soon.

 

On 2016-06-05 by Jim

Thanks for the response and insight. The unit has quieted down significantly over the last 24 hours of operation with the condenser coil assembly now not having nearly as many moments in movement/vibration. These moments are also now more in synchronization with the enclosure movements.

The only changes I have made so far is in three (3) small refrigerant charge reductions based on superheat readings at the compressor return inlet. I am suspect there was/are possible refrigerant condensation fallout occurring inside the low pressure return line despite the pressure readings being stable with only very small fluctuations indicated in the high side discharge line.

The HS head pressure and LS pressure ratio is well within declared limits stated in the manufacturer's setup specification documentation.

I am considering adding a liquid line-trap loop in the low pressure piping near the evaporator outlet to see if it makes any difference in the vibration. I will post my findings. What is your opinion on my thoughts and direction? Thx, Jim

Reply by (mod)

Interesting; check that nothing remains loose.

Indeed refrigerant on the low side, as you know better than I, can at worst ruin a compressor and less bad, might cause ugly noises. Interesting and clever thing to try - slight charge reduction. Thanks for keeping me posted; working together makes us smarter.

 

Very noisy and vibrating new Goodman Split System HVAC unit - expert tech seeks more info

I have a new Goodman, 14 SEER, R22 scroll-compressor, Split-System HVAC unit that was purchased/installed in 2009 but not put into service and started until today.

The unit cools my home very well however the condensing unit is very noisy and has a great deal of vibration in the low side refrigerant line and the condensing coil is physical moving about a lot inside the housing in perfect time with the vibration.

The ambient temperature was/is 105F with the HS press @ 250psi and the LS Press @ 78psi which yields an evaporator coil temperature of around 43F.

The pressure readings are stable with no fluctuation what-so-ever.

I am a certified tech with over 25 years of experience and I have never seen a unit do this before now.

Anyone have any experience with this problem and/or any advice? Thanks a bunch, Jim On 2016-06-04 by Jim

Reply by (mod)

Jim

Look first for loose mounting bolts or screws anywhere on or in the compressor/condenser unit; also look for refrigerant tubing left un-insulated and in contact with a vibrating service. You probably already know those common noise sources and have perhaps more field experience than I do, so let's think and argue about this a bit.

Only a mechanical movement can cause vibration; we can probably exclude outside influences such as wind or nearby mechanicals on other systems;

Is the pad level and secure?
Can you take a mechanic's stethoscope and check components for vibration: seems to me we have either the compressor motor or the fan motor. I don't think that even a bad control such as a relay or TEV would vibrate at such a high frequency as to cause the noise you describe.

I'm speculating you'll trace the noise to the compressor motor itself: perhaps a sticking valve. I did some research on vibration in rotary compressors: you'll want to use Google Scholar to search for and find these articles:

Imaichi, Kensaku, M. Fukushima, S. Muramatsu, and N. Ishii. "Vibration analysis of rotary compressors." (1982). - you can read this directly at http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1406&context=icec it's very technical, but the conclusions are worth noting. It makes me want to check the stability of the voltage being delivered to the unit; if that's ok it makes me suspect the motor itself is bad.

Also

• Kim, Dae-Kyong, Kwang-Woon Lee, and Byung-Il Kwon. "Commutation torque ripple reduction in a position sensorless brushless DC motor drive." Power Electronics, IEEE Transactions on 21, no. 6 (2006): 1762-1768.
• Ishii, Noriaki, M. Fuhushima, K. Sano, and K. Sawai. "A study on dynamic behavior of a scroll compressor." (1986).
• Lee, Ho-Jung, and Kwang-Joon Kim. "Multi-dimensional vibration power flow analysis of compressor system mounted in outdoor unit of an air conditioner." Journal of sound and vibration 272, no. 3 (2004): 607-625.
  
  The presence of these and other research papers to me as a non-engineer, suggest that vibration in rotary or scroll HVACR compressors is a known and studied problem.
  

 

Question: copper refrigerant pipe vibration

(Feb 6, 2014) Lee Albro said:

I have two HVAC systems with heat pumps. The copper pipe (heat) that comes out of one unit vibrates alot and causes noises in the house. It is an upstairs unit and I had the vibrating pipe ran up outside the house, into the attic and down to the upstairs unit.

It still vibrates and makes noises. Is there something that can deminish the vibration after it leaves the unit and before it reaches the house?

Reply:

Lee, that vibration doesn't sound good - as it can cause a wear-leak, refrigerant loss, heat loss, or other equipment damage.

You could install foam insulation around the piping (it should be insulated anyway) where it passes through openings or needs buffering, but I'd suggest asking a service tech to diagnose and fix the vibration - hoping to avoid a more costly problem.

...

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

Or see HVAC SYSTEM NOISE DIAGNOSIS FAQs-4 - more-recent diagnostic questions and answers about heating and cooling system noises and sounds

Or see these

HVAC Noise Diagnosis Articles

• HVAC SYSTEM NOISE DIAGNOSIS - home
  • CHATTERING RELAYS, HVAC EQUIPMENT
  • DUCT SYSTEM NOISES
  • DUCT VIBRATION DAMPENERS
  • FAN NOISES, HVAC
  • HVAC SOUND DESCRIPTIONS
  • HVAC NOISE-1 BANG BUZZ VIBRATE - banging, bearings, buzzing
  • HVAC NOISE-2 CHATTER CLANK FAN GROAN - chattering, clanks, clunks, cyclical, fan, groans, growls, honking
  • HVAC NOISE-3 HISS HOWL HUFF HUM - hiss, howl, huff, hum, groan, woo wuu wuff
  • HVAC NOISE-4 POP, RATTLE, ROAR, RUMBLE - loud start, pop, rattle, rumble, water, silence
  • HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU - scream, sing, squeal, trumpet, wawa, wowo, water gurge, whine, whistle, wuwu
  • NOISES, HVAC SOUND RECORDINGS
  • REFRIGERANT PIPING GURGLING

Common HVAC Failures that Cause Noises

• BURNED-OUT COMPRESSOR
• CAPACITORS for HARD STARTING MOTORS
• CONTACTOR RELAY DIAGNOSIS & REPAIR
• CONTROL CIRCUIT BOARD, A/C
• COPELAND ELECTRICAL HANDBOOK [PDF]
• CRANKCASE HEATERS
• FAN, COMPRESSOR / CONDENSER UNIT
• FAN NOISES HVAC
• HARD STARTING COMPRESSOR MOTORS

Suggested citation for this web page

HVAC SYSTEM NOISE DIAGNOSIS FAQs-3 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING NOISE DIAGNOSIS

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