AC Noises

AC Noises

Is your air conditioner suddenly making strange noises?

Do not ignore changes in the sounds coming from your AC system. These new sounds often indicate a problem with your AC system.

When working efficiently, your air conditioning system should make minimal noise. If your air conditioning system is making an unusual sound, it may be time to call your local HVAC professional to assess the issue and provide necessary repairs. While some light noise or humming is normal, below are a few noises your air conditioner should never make.

7 Common AC Noises & What They Mean

Noisy air conditioners aren’t only a nuisance, but they can be signs of something problematic lurking deep within your air conditioning system. While not all noises are created equal, here are a few sounds your air conditioning system should never make:

1. AC Making a Buzzing Noise

If your air conditioning system is making a buzzing sound, there may be an electrical issue.

A buzzing noise is almost always indicative of an issue with:

  • Condenser fan motor
  • Contactor relay switch
  • Sign of loose wiring

Because electrical issues may be dangerous, be sure to turn off your air conditioner right away and call a professional.

2. AC Making a Hissing Noise

A hissing sound emitting from your air conditioning system may be indicative of a refrigerant leak from either a line or coil.

It’s important to get this issue addressed right away, as refrigerant is both expensive and necessary in order to cool your home. Refrigerant leaks can be dangerous too, so make sure you enlist the help of a professional to diagnose and assess any issues.

3. AC Making a Squealing Noise

If your air conditioning system has started to squeal, you may need to replace the belt. Replacing the belt on the blower is an easy repair that should be replaced quickly before the belt breaks and your HVAC system stops operating. Your local HVAC professional will be able to fix a faulty belt in no time.

4. AC Making Loud High-Pitched Squealing Noise

A very loud and high-pitched squealing noise is usually indicative of high internal pressure. High internal pressure can build up inside of the air conditioner’s compressor. Although compressors usually have a sensor that will signal the air conditioner to shut off if the pressure gets too high, if it doesn’t, the pressure could rise to a dangerous level. If your air conditioner is making this noise, be sure to shut your AC off right away.

5. AC Making Rattling, Thumping, Clanking or Banging Noises

If a rattling or banging noise starts coming from your HVAC system, chances are something is loose or has broken and is now being blown about the condenser unit. It may be something as small as a nut or bolt, but in some cases, it could be a fan blade. In any case, turn off your HVAC system and call a professional technician to take a look.

A rattling noise and any other thumping, clanking or banging sound is usually indicative of an issue with the assembly motor or blower. Rattling may mean that a small component of the air conditioning system has come loose and is flying about the unit. If this is the case, it should be an easy fix. Simply shut off your air conditioning system and check to see if anything has come loose, broken or been disconnected.

6. AC Making a Clicking Sound

When your HVAC system turns on or off, light clicking sounds are completely normal. However, if you hear a loud clicking noise while your HVAC system is operating, something could be wrong with the relay or an electrical control. In this case, it’s best to schedule an inspection with an HVAC professional to prevent further damage to your air conditioning and heating system.

7. AC Making a Thwapping Sound

This sound is similar to what playing cards make when slapped against the spoke of a bicycle. It is most likely an indication that something is stuck in the blades of the blower. This is not a huge problem, but if the blades are not cleared, the motor will be subjected to unnecessary wear and tear and will have to be replaced sooner.

Where Is the Strange Noise Coming From?

Where you hear the noise can make all the difference. The location of the sound will usually tell you what problem you are facing. The most common air conditioner noises come from the outdoor compressor unit, the ductwork or the air handler.

Here are some of the most common issues that could be making noises in your AC.

Outdoor AC Compressor Making Noises

This is the large AC unit that sits outside your house. The compressor unit is responsible for cooling your air and sending it throughout the house. Being outside, your compressor unit is prone to a variety of issues.

  • Banging sounds can signal a costly repair. It is usually evidence of a loose connecting rod, crankshaft, or piston pin.
  • Buzzing can mean your AC has a bad connection, loose or burned contactor.
  • Clanking indicates the compressor itself may have become loose.
  • Hissing is often accompanied by bubbling noises. It’s a sign that you may have a refrigerant leak.
  • Humming means your motor may not be starting or it’s starting slowly. This could mean you need a new capacitor or that the compressor motor has failed.
  • Screeching is a sign of a very serious problem. Turn off your system immediately and call an HVAC technician. Dangerous amounts of internal pressure may have built up inside your compressor.

Noises in the Ductwork

Your ductwork carries the air all throughout your house. Unfortunately, it also carries sound. Your air ducts can amplify sounds coming from either the ducts themselves or other parts of your HVAC.

  • Buzzing from your ductwork can signal that bees or wasps have gotten into your ducts. Animals often find their way in, so fluttering or scratching noises might indicate some other critter has taken up a home in your ducts.
  • Rattling means you may have a bad blower or fan.
  • Whistling indicates the ductwork is simply contracting as air moves through it.
  • Hissing could signal a leak letting air out of the ductwork.

Noisy Air Handler

You know that creepy noise coming from your attic or basement? No, it’s not a ghost, it’s probably just your air handler. When not functioning at its best, it can cause a variety of spooky noises. So before you call Ghostbusters, call an HVAC technician to see if it could be one of these problems.

  • Buzzing signals electrics on your air handler are wearing out. You may be in need of a new relay switch or electrical work on the circuit breaker.
  • Clanking could mean the compressor or condenser hardware may have come loose, or you just have a bad compressor.
  • Hissing is another sign that you may have a refrigerant leak.
  • Ticking occurs when debris might have gotten stuck in your fan blade.

Ignoring the weird noises from your AC can turn minor issues into major expenses. As soon as you hear something that does not sound normal, contact a local HVAC technician to help. And remember, the best way to prevent a noisy air conditioner is by having regular, annual maintenance check-ups.

7 Replies to “AC Noises”

  1. Thank you for informing me that the fan belt might be in disrepair if it is making a squealing sound and it should be replaced quickly. I was taking my daughter to ballet practice yesterday when I heard a weird noise coming from the AC that is near the garage. It did not sound good; it kind of sounded something between a chirping and a squealing sound. I don’t know anything about ACs so I will have to look for repair companies in my area who could help me.

  2. My aunt has noticed that her AC has been making a buzzing noise but she doesn’t know what it is from and it is inside. I’ll be sure to tell her that she should look and see if it comes from the outdoor unit, the ductwork or the air handler because the location can show what is wrong. It could be really useful for her to get a professional to take a look at what is wrong and how to fix it.

  3. My friend told me that after activating his air conditioning unit last night, he noticed that it started making a weird rattling noise for an hour, and then it disappeared. I had no idea that the cause of this could be a loose part inside the unit. I’ll share this with my friend and suggest that he do a turn it on and off first. If that doesn’t work, I’ll suggest that he contact an air conditioning repair expert.

  4. I’m glad you mentioned that a hissing noise coming from our air conditioning could be due to a leak in the refrigerant line. I noticed a soft hissing noise coming from the general area of my home’s AC unit when I was gardening this morning. Thanks for teaching me how to discuss possible causes of the issue with an AC repair service soon!

  5. The fact that screeching can mean a very serious AC problem was quite alarming to read. We initially thought that the screeching we’ve been hearing was from something else, but when we realized it was coming from our AC, we didn’t know if we should continue using it or not. I’ll have an HVAC contractor stop by and repair it first before we even think of turning it on again.

  6. I find it alarming that if your air conditioner is making a hissing sound, you might leak its coolant. This is happening to my aunt’s unit a random, and she’s not sure what to do next. We’ll look around for an expert who can get this fixed before it turns into something even serious.

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