Air conditioner or heat pump noise diagnosis & cure questions & answers:

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

This air conditioning repair article series 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 shrieking and howling or death-rattles that sometimes (not always) presage costly compressor damage indicating air conditioning compressor or A/C compressors at or near end of their life.

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.

 

Why is our central air conditioner/heater making smoke and a loud noise?

Why would smoke and loud noise be coming from central heat/air unit - On 2015-01-12 by Bonnie

Reply by (mod) -

Watch out: A fire or electrical components overheating and burning up: SHUT THE SYSTEM OFF IMMEDIATELY.

If you can't safely do so at the equipment's local shut-off power switches do so from the main electrical panel.

If smoke and noises continue you'll need to get out of the building and call your fire department.

If they stop then you can call your air conditioner repair service.

 

Diagnose loud thunder noise or banging on our roof - coming from ceiling vents

Last evening I had the heat on when my husband got home cuz he works third shift he turned the heat off and put the air at 71 as we live in Florida

He went to bed about 4:30 this morning he said at 8:00 a.m. he was awoken as was my 10-year-old son by a very loud thunder like noise or like somebody was on the roof banging.

There was no thunder it was sunny out.

He said it was only in like our bedroom and our boys' bedroom which is located on the far right side of the house which is also where the outside unit is located.

He said he went outside there was nothing. The noise was basically coming from our ceiling and the vents that are up in our ceiling.

He turned off the air and the noise stopped.

He waited a few minutes and put the air back on and it hasn't made that noise since so we're curious as to what this could have been because the noise was so loud that it woke a couple people up.

They said that it sounded like there was really bad thunderstorm or someone was actually on a roof banging.

If anyone could possibly tell us what this might have been or could be please let us know as we're not very acquainted with these types of things with the HVAC systems thank you we appreciate it On 2020-11-26 by Angela -

Reply by (mod) - failing HVAC equipment

Angela

Thanks for the interesting AC/Heat pump noise question.

The compressor motor in some heat pumps or air conditioners (in the outside unit) can have trouble re-starting if switched "OFF" and then immediately back "ON" - because the motor is trying to start against a high head pressure of refrigerant.

Newer equipment often includes a safety control that simply prevents re-starting right away but older equipment may not have that feature.

That might be what you encountered: the motor, unable to start, was making a horrible racket.

That can also damage the compressor motor. So don't do that again.

If the system is working ok now you may have been lucky and avoided serious damage; else you'll need a service call.

Condenser switch stops humming when tapped

There is a switch I think in the condenser and if I tap it it stops humming unnoticed wire was loose on it.

Every time I put it back on it hums and pops off . Is it the switch or is that a safety thing that does that to prevent more damage from another part. - On 2020-07-30 by Stephen borden -

Reply by (mod) - replace failing HVAC relay

You are describing a control relay that is failing and needs to be replaced.

High pitched sound from freon line on my Payne air conditioner

I have a payne air conditioner. Very high pitch coming from freon line. Guys that came said psi is normal - On 2019-08-03 by Wendy weimer

Reply by (mod) -

Wendy

often the noise we hear at a refrigerant line is being mechanically transmitted from an HVAC motor or component nearby.

It's also possible that a refrigerant line is partly blocked or a refrigerant metering valve is malfunctioning

also

In the CONTINUE READING or RECOMMENDED ARTICLES see these two diagnostic start points for a high -itched whine or noise in HVAC systems

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

HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU - scream, sing, squeal, trumpet, wawa,

Small blue box atop our Rheem 90 unit keeps making noise after the unit is turned off

we have a very old Rheem 80 unit. there is a small blue box that sit outside of the unit. It "runs" a long time after the unit turns off.

What can we do about this noise? Sometimes we just shake the box and it stops. - On 2018-07-06 by connie

Reply by (mod) -

Sounds as if there's a worn relay or control or fan limit switch that needs replacement.

This isn't something a homeowner can fix herself unless she's a trained service person.

Call your HVAC repair technician.

Question: heat pump makes a metallic noise

The heat pump makes a metallic noise constantly, even if outside is 16 gr C. I am sure it is not ice. On the contrary, when the A/C is on, the metallic noise disappear. The heat pump is now 3 yrs and it was noisy from the beginning.Does anyone have any idea? Thank you so much! (Sept 28, 2015) Laura said:

Reply:

Laura, see RATTLING & vibration noises from A/C or Heat Pump System

Laura: Your service tech may want to check the reversing valve.

 

Question: tapping sound in wall where refrigrant piping runs

I have 10 year old heat pump where the interior unit is located in the attic, the exterior near the house, and the coolant pipe is run through the exterior wall of the house to connect the two units. Over the past couple of years there has been a "tapping" sound in the wall where the coolant pipe is located.

That tapping does not occur when the unit is running and stops about 5 minutes after I turn the unit off. I have checked the condensation pipe and it is not that. Any ideas? (Feb 14, 2016) Don said:

Reply:

Don:
Could we be hearing movement of the piping through a tight opening or across a surface due to thermal expansion / contraction as the refrigerant piping temperatures change?

 

Question: American Standard unit Clicking noise

My American Standard unit outside is clicking, it turns on, Clicks turns right back off or on. It does this for 2-4 times then it will run for a couple minutes. Then it repeats the cycle. I have it onow video any suggestions? (Aug 6, 2016) Kelly said:

Reply:

Kelly please see CLICKING SOUNDS from air conditioner or heat pump system, then see our discussion of chattering relay switches and controls

at RELAY CONTROL SWITCHES and let me know how that works for you and your service technician.

 

Question: loud blower unit, loud snapping and clicking noise

I am in a brand new build apartment with a Goodman air conditioning unit. The blower is extremely loud, and there is an extremely loud snapping and clicking that happens whenever the unit kicks in. The sounds are coming from just behind the filter in the main vent to the living room.

I have had the guy who installs the units look at it and told me it was the condenser coil making the noise and there is nothing he could do about it. Other apartments have also complained. The guy across the hall has to sleep with the bedroom door closed.

I have not gotten a single night's sleep since I moved in here due to this noise. What can I tell them needs to be done to correct the noise. If I had this installed at my house, I would have had it ripped out the next day. I haven't read anything yet that seems to be something that I can take to this guy that denies that the noise can be fixed. Thanks in advance for any help you folks can give! (Sept 5, 2016) Anonymous said:

Reply:

Anon there are two different concerns that occur to me:

1. The blower speed and sound and air velocity vs. duct design, insulation, requirements, and perhaps soundproofing between you and the AC unit

2. Loud clicking and snapping that you hear in, at or near the air handler or through nearby HVAC ducts, especially when the blower unit first starts are often traced to a very excited electrostatic air cleaner who is zapping dust particles loosened when the air flow starts up.

 

Question: loud banging noises coming from our A/C unit and constant cut off of the air supply

I am frustrated as well with loud banging noises coming from our A/C unit and constant cut off of the air supply through the vents while the outside fan spins aimlessly. We have had 2 service calls with 2 different technicians only to be told they could not tell the problem but charged us anyway for each service visit. I even went so far as to record the banging sound on my phone. Please help!! my email is jasonericbillz@gmail.com - Sept 7, 2016) Jason B. said:

Reply:

I'd give the service manager a call and ask for a more-experienced technician.

Also be more specific about where the noise is occurring: outdoor unit, indoor air handler, ductwork.

Followup: Anonymous said:

Thanks for that response. the noise is coming from directly inside the main vent in the living room. That vent is located a few feet from the indoor unit located in the ceiling of the bathroom.

I have had 2 men look at the unit and still tell me and other tenants that the noise is the condenser coil making the noise and it only happens when the unit kicks on. That is true, but it is so loud that it can wake me up out of a deep sleep.

I can't believe that that is acceptable. Why would the condenser coil make that noise, and is it possible for the condenser coil to do that? I'm at a total loss.

Thanks for any further information you and/or others might be able to offer.

Reply: give the service manager a call at your HVACR repair company; politely explain the problem and ask for help from an experienced service technician.

 

Question: vibration noise after fan replaced

I had my fan replaced on my outside condenser , heat pump. Now, there is more noise and vibration than before, I had to put foam between top grill and frame. It is a 4 ton unit and he put in a 1/2 HP 1075 rpm motor. He said it is because my last motor was a piece of crap. Does this sound like the right size motor. thanks 2016/09/15 Steve said:

Previous question error. He put in a 1/3 hp motor, not 1/2 hp, thanks

Reply:

Perhaps more noise and vibration from improper mounting or an unbalanced fan blade set? Look for loose parts first.

Unless the fan is running at the wrong speed, I would not expect fan vibration and noise to be due to motor size.

Rooftop ac/heater is making buzzing noise

My rooftop ac/heater is making buzzing noise. I read several of these articles and they do not seem to match my situation. I have a payne unit. The noise seems to be coming from the compressor coils, even when all power is secured. It will buzz for 4 or 5 seconds, and stop. This happens on and off randomly.

The noise is not at the compressor, but the upper copper coils. I dont suspect any leaks because the air conditioner does work great otherwise, and if there was some sort of leak the unit would not be working anymore.

The noise does not have any thing to do with contactors or motors, or capacitors. I have replaced all of those, and they all work.

The noise does not come from those parts anyway, and the noise should not be present when there is no power. This gets annoying when I go on roof to wash down my solar panels. On 2014-11-26 by Mark

Reply by (mod) -

Mark I agree you want this buzzing diagnosed but I'm unclear from your note just what might be going on.

1. are you saying the buzzing happens when power is off?

2. you are sure buzzing is not from any of the electrical components - I'd look again as relays often are a buzzing noise source as are failing motors. A loose electrical connection can also be a noise source as well as dangerous.

3. Check motor mounts and all other mechanical fastners. Try pressing on the exterior of the access panel or door or cover when the equipment is buzzing.

4. Check for a bad fan bearing

Carrier ac lost refrigerant due to lighting strike - now its noisy

New Carrier ac lost refrigerant due to lighting strike nearby. Energy cracked refrigerent line to AH. Charged condenser now a bit noisy. Sounds like startup hum, but constant. Ideas? On 2014-10-04 15:23:01.557150 by Charley

Reply by (mod) -

Sounds like a compressor problem, Charley. A failed refrigerant metering valve could also be keeping high pressure on the high side of the system even when the system is off, or the power surge could have damaged control board, relay, or motor.

What caused a loud explosion sound from my heat/air unit outside

I heard a loud explosion sound from my heat/air unit outside. now it will not come on at all - On 2014-09-16 by Anonymous

Reply by (mod) -

Sounds like your AC system blew a fuse, circuit breaker, compressor motor or other component.

Watch out: Leave the power OFF completely to the system and call an HVAC technician for repairs.

When the air handler fan is on a high pitched whine comes into our bedroom

A new Lennox air handler system installed yesterday. When the fan is on, a high pitched whining noise comes through the bedroom only.

Taking out the filter stops the noise. Filter is supposed to be 18" by 24" and that's what's in there. But there is quite a bit of space between the edges of the filter and the channel it fits in.

My earlier air handler, also Lennox, was very quiet except one time when the filter collapsed and the whining sound came back, only in the one duct.

Replaced the filter and everything was good. Installation company is not sure what the problem is. Any clues? On 2014-09-13 by J Smith -

Reply by (mod) -

J S

Since the noise is just in one area I don' think this is the fan unit itself; try looking for a return duct air leak

Followup by JS - why would the whining stop when I changed the filter

I will, but why would the whining stop when I changed the filter in the previous air handler?

Reply by (mod) -

Anon re whining ductwork

Dirty air filters reduce air flow, creating more negative pressure in the return duct, thus possibly increasing noise at duct leaks.

OR the noise is actually originating at air leaks around the air filter itself.

Thunder rumbling from my air conditioner

Hi DanJoe, I still have the rumbling in my YORK 2-speed motor AC system. It has gotten worse, and louder.but I haven't called the technicians who installed it because, sadly, I don't have much confidence in the ones who have come out in the past and don't know how to find a really competent one from another company.

The rumbling, like thunder is coming from the inside air handler, and goes on for anywhere from 30 seconds to a minute before the fans kick in. There are 2 speeds and I've been trying to figure out if that is involved in the problem.

It's very nerve-wracking hearing this noise when the unit itself is sooo quiet; that being the reason I chose it. Do you think I'm risking permanent damage to something by stalling getting a repair person in here? Thanks to you and anyone out there who can help me! On 2014-08-13 by Ginger Vela

PS sometimes the rumbling goes on a bit after the one fan speed comes on.

Reply by (mod) - success with the quality-of-service problem by speaking politely with the service manager

Ginger,

I've had success with the quality-of-service problem by speaking politely with the service manager at the company you use.

Explain that the problem has been looked at with no satisfaction, that it's getting worse, and that perhaps it might even be unsafe - ask that an experienced senior tech be sent to your home. Let me know what ensues.

I suspect they're going to find a bad air handler motor or loose HVAC ductwork metal.

Followupby Ginger Vela

First of all, thank you for your response which I just read. This morning I called the company that installed my unit and a very familiar tech came out within an hour.

I set the system to kick on when he arrived, and he HEARD the noise! His diagnosis; a failing motor. This unit has an *ECM motor, and one is on order for me.

Luckily, it is still under warrantee, and I will only have to pay for the labor. I've had bad luck with the functioning of this model which needed a new compressor which started failing about ONE YEAR after its installation in 2009 and now this motor failure issue.

It's called York Quiet Drive model It cools great and is beyond belief as far and quiet and efficiency go, except for the nerve-wracking noises of failures of those two components. I am so relieved to know what's wrong and to be able to get it fixed.

Unfortunately, my cooling savings have been offset a bit by the installation/labor chg. for the new compressor of $767.50, +a new evaporator coil in 2012, and now whatever the labor is for this motor. I'm told it will be a lot less than the compressor install.

Thanks so much for your help and encouragement. Just so you know, there is no service mgr., and the owner/ salesperson made himself scarce once the initial job was done, only once agreeing to speak with me on the phone at my insistence. Sincerely, Ginger

I will ask him. Thank you. I wondered about that as we do have fluctuations sometimes. The power Co., Florida Power and Light, is always trying to sell surge protection. I also have a SMART METER, (against my will) and did suspect it in the lose of the compressor.

I HAD it switched out for an old-style meter, and this motor problem started BEFORE FPL pretty much forced us have the SMART METERS reinstalled this May or else PAY a surcharge each month.

Will definitely ASK. Also, I have a very old house which does need an electrical upgrade. 1936 house.

Don't like the thought of it being all torn up for that work! Will keep you posted. Thanks GV

Followup by GV

DanJoe, The technician came out again, and I now have a new air handler blower motor.

System is working well and so much quieter. He did not think fluctuation in power was a likely cause since there are safeguards against it in the unit. Thanks, Ginger

Reply by (mod) -

Thanks for the follow-up GV - that will assist other readers.

Daniel

Reply by (mod) - York Quiet Drive

Thanks for the follow-up GV - it will help others.

YOu might ask the installer to check for any conditions that might contribute to early motor failure such as voltage variations.

Success with the quality-of-service problem by speaking politely with the service manager

Hi , The compressor on my 3 Ton Amana A/C unit starts after 5 minutes of fan start ( there is no delay relay ) .. cold air blows out from top of the unit ..
and

looks like compressor tries to start couple of times and finally starts on 3-4 try and then it works normal .. On 2014-08-09 by PKG

Any advice will be appreciated.

Reply by (mod) -

PKG

Sounds like a hard-starting compressor, possibly a failing compressor motor, possibly aided for a time by a hard-start capacitor kit.

My ac unit makes a squeal or whistle.

My ac unit makes a squeal or whistle.

I will hear the fan motor turn on fine and then right before fan blower up in roof turns on it will make the noise and then also right before turn off.

Don't know what it is. I just bought this brand new unit 4 mo ago and its never made this noise before. On 2013-04-03 by sarah

Reply by (mod) - My ac unit makes a squeal or whistle

Sarah squealing compressors are discussed e at Squealing air conditioner and heat pump equipment, diagnosis

HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU - scream, sing, squeal, trumpet, wawa, wowo, water gurge, whine, whistle, wuwu

Loud Thumping sound from LG A/C Unit

When my L.G 1.5 ton strip A,C. whenever it is switched off after half an hour running, makes a loud thumping sound. What is the likely reason for this heavy thumping sound Please? Can u tell me?

On 2013-03-10 by Valerian

Reply by (mod) -

Valerian,

Thumping A/C equipment doesn't sound good. But first we need to know what's thumping; could be components that are loose, or something else.

Start by seeing if you can trace the noise - to the indoor or outdoor components to start.

Upon start up, the a/c makes a rip cord like sound.

Here's a flabergaster. We have had 5 techs now to look at our A/C unit and no one has ever heard a unit make this noise in all the 20 or 30 years they have been a tech. This all started 2 weeks ago when we had a solar panel installed on our water heater and the NEST thermostat on our unit.

Upon start up, the a/c makes a rip cord like sound. Like a rigid piece of plastic is being pulled through a tight spot, or - well - someone cutting a very bad, gassy fart.

It ONLY does this after the system has completed its OWN cycle and at start up. We have had a blower wheel and motor replaced.

Found a piece of cardboard stuck in the system and the tech will be coming out tomorrow to inspect it again.

Someone suggested it might be our HEPPA filter, but we took it out for 2 cycles and it still made this horrible noise.

I think whatever damage has been done to our system is now not only affecting the handler but is now affecting the unit outside. Any help and suggestions are welcome. On 2012-09-13 by Teresa -

Reply by (mod) -

Teresa

Use the contact us link at page top or bottom to send us a reording of that odd noise - it may permit further comment.

Loud screeching noise from air conditioner

Just had my ac fan motor replaced 2 days ago. System ran fine since then. This morning I heard the system kick on and heard a screeching sound from the compressor. I went outside to see the fan trying to spin. I shut the system off, waited 10 minutes and turned it back on. The compressor fan was spinning but was making a EXTREMELY LOUD SCREECHING sound so I turned if off. What could this be??

Just had my ac fan motor replaced 2 days ago. The system was running great since then. This morning the system kicked on and the compressor was making a screeching sound, so I went out side to see the fan 'trying to spin'.

I shut the system off, waited 10 minutes then put it back on.

The fan was spinning but it was making a EXTREMELY loud screeching noise, so I shut the system off. What could it be? On 2012-09-11 by mrr2ro - On 2012-07-18 by Debi -

Reply by (mod) -

Debi, screeching and squealing are described in HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU - scream, sing, squeal, trumpet, wawa, wowo, water gurge, whine, whistle, wuwu

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.

There is also "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.

Buzzing noise at Carrier Performance Series A/C unit Model # 38TXA060350

I have a Carrier Performance Series A/C unit Model # 38TXA060350. During the cooling cycle, when the compressor kicks in, there is a buzzing noise coming from the compressor and continues until the cooling cycle ends.

If the noise was just outside it would not be such a problem, however, the noise follows the lines into and thru our basement and is very irksome. What is the problem, the solution, and is there a way to mitegate the noise?

thanks,
jim On 2012-07-14 by jim -

Reply by (mod) -

Jim, take a look at the text near the top of this article and you'll find a live link to buzzing noise diagnosis cure;

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

Loud clicking/ clanking noise from the outside heatpump/condensor unit

Our system all the sudden started acting up. noticed only warm air coming out of the vents inside. checked thermostat and it had nothing on the display(like it was off).

I heard a loud clicking/ clanking noise from the outside heatpump/condensor unit. Went outside and the noise was coming from where the wiring went into the side of the unit. the fan was still running on the unit. I can smell some electrical burning smell. I shut off the system by hitting the circut breaker...help. loud clicking/ clanking noise from the outside heatpump/condensor unit On 2012-06-26 by Need Help

Reply by (mod) -

Watch out: MOST IMPORTANT: if you smell something burning, turn off the equipment immediately and leave it off. If there is further evidence of a fire or smoke, get people out of the building and call your fire department.

When your thermostat shows nothing on its display, start by checking to see that the indoor heating or cooling equipment has power - often you'll find that it has been switched off or has perhaps tripped a circuit breaker or blown a fuse.

If the equipment has power, next I check for loose or damaged thermostat wires or a bad thermostat transformer.

When you hear a loud clanking at the outside compressor/condenser unit the news sounds worse - often that is an indicator of a failing or failed compressor unit. You need a service call by an experienced HVAC technician.

See also our noise sources

at CLICKING NOISE DIAGNOSIS & CURE

...

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-2 - more-recent questions and answers about noise in heating, air conditioning, or venting systems

Or see these

HVAC Noise Diagnosis Articles

• HVAC SYSTEM NOISE DIAGNOSIS
  • 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

Or see this

List of 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 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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