Reasons Why An Air Conditioner Is Making A Whistling Noise

Owning an air conditioner can be great, but it can get slightly annoying if it starts to make a whistling noise every time you use it. If you start to notice your air conditioner is making a whistling noise, don’t just ignore it and hope it goes away, look into the issue yourself or have a professional do it for you.

There are a few common reasons why an air conditioner is making a whistling noise, and they are dirty air filters, closed dampers, blocked return vents, or too many closed doors. So, in other words, the main reason an air conditioner is making a whistling noise is mostly due to airflow issues.

Even though your air conditioner is making a whistling noise, this problem is usually very simple to fix yourself, and it usually does not cost a dime. In this article, we will be going through the reasons why an air conditioner is making a whistling noise and explain how to fix this problem.

Why is my Air Conditioner Is Making A Whistling Noise?

Most of the reasons an air conditioner makes a whistling noise are due to problems with airflow, but there are a few other reasons an air conditioner is making a whistling noise that requires a professional to fix.

Airflow IssuesProfessional Issues
Blocked or closed vents: This happens when vents are blocked by furniture or other objects.Leaky ducts: The ductwork may have some small cracks or openings that air can pass through.
Dirty air filter: A dirty air filter can restrict airflow due to becoming clogged with dirt and other debris.Lack of return inlets: The air conditioner will not function properly without return inlets.
Debris in ducts: Lots of small objects can find their way into the air conditioner vents restricting airflow.Too small return grille: With too small return grilles, there is not enough air recirculating back into the air conditioning system.
Fully or partially closed dampers: If one of the dampers has been closed or partially closed, it can prevent air from going to certain parts of the house.Oversized system: An oversized air conditioning system moves too much air for the ductwork to handle.
Too many closed doors: If there are too many closed doors in the house, then the air can only go under the doors to the return vent.Malfunctioning blower: There could be a problem with the fan or belt in the air conditioner.

Ways To Fix The Whistling Noise The Air Conditioner Is Making

As mentioned above, there are airflow issues that can easily be fixed by you, but there are other issues that must be fixed by a professional. Here are the ways to fix the whistling noise the air conditioner is making:

Airflow FixesProfessional Fixes
Blocked or closed vents: Move all objects that are blocking air vents and open any closed vents.Leaky ducts: A professional will fix the leaky ducts by sealing any cracks and ensuring all ducts are properly connected and insulated.
Dirty air filter: Change or clean the air conditioners’ air filter every three months or every month in the summer.Lack of return inlets: A professional will install a return inlet, or a few, depending on how much air the air conditioner needs to process.
Debris in the ducts: Check all of the air ducts for any debris and remove the debris promptly.Too small return grille: A professional can increase the size of the return duct and grille.
Fully or partially closed dampers: Find the dampers by the indoor unit and open them fully.Oversized system: A professional can either install additional ductwork or they can replace the air conditioner.
Too many closed doors: Try to keep doors open in your house whenever possible.Malfunctioning blower: A professional can either try to fix the blower or replace the blower motor.

Other Noises To Listen For Coming From The Air Conditioner

Aside from a whistling noise, your air conditioner might make other noises that can be quite concerning. Here we will go through some additional noises, what they mean, and how to fix them.


A clanking noise coming from your air conditioner usually signifies an out-of-balance or loose part and should not be ignored because it can cause bigger problems.

How to fix this issue: 

If you can hear clanking coming from your air conditioner, you could turn it off and try to address the problem yourself, but it would be better to have a professional look at it so they can fix the problem properly.


A buzzing noise coming from your air conditioner typically means there is an electrical problem, but it could also mean loose parts, the air filter is dirty, there is a refrigerant leak, and so on.

How to fix this issue: 

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You can check the air filter to ensure it is clean, and you can look for a refrigerant leak. If you notice there is a refrigerant leak or if you cannot tell, then you will need to contact a professional to find and fix the problem.


A hissing noise coming from your air conditioning system usually means a refrigerant leak, but it could also signify a duct leak or an ill-fitting air filter.

How to fix this issue: 

You will have to call a professional to take a look at your air conditioner if you hear a hissing noise since it is most likely a refrigerant leak or a duct leak. However, before calling a professional, check to see if the air filter is fitted properly.


If you hear a banging sound coming from your air conditioner, it could mean there is a loose or broken part that needs to be replaced right away.

How to fix this issue: 

A professional would need to look at your air conditioner to confirm if it is a broken or loose part that is making the banging noise, and if it is, they can repair it.


If the clicking noise is constant when the air conditioner is running, it could mean there is a defective control, or a small object has found its way into the blower fan.

How to fix this issue: 

Before you decide to call a professional, you can turn off your air conditioner, then look for any objects or debris in the blower fan. If you cannot find anything, then the next step would be to call a professional and have them take a look and fix the issue.


If you can hear a rattling noise coming from the outside air conditioning unit, then it could mean something is coming loose inside it, or there is debris in the unit.

How to fix this issue: 

If the sound is coming from your outside air conditioning unit, then you can turn it off and clean off any debris that you find. If cleaning the outside unit does not help, then you should call a professional so they can check both the inside and outside units to find the problem and fix it.

How To Tell When It’s Time To Buy A New Air Conditioner

There are a few different ways to tell if it is time to purchase a new air conditioner, and we will go through each of them now.

  • Diminished airflow: If you notice there is a significant decrease in the airflow your air conditioner is putting out, then it could mean the air conditioner’s compressor is beginning to fail.
  • Inconsistent temperature: If the air conditioner is still putting out the same amount of air, but it is not cool, or it is only cool in certain rooms, then it could mean you need to purchase a new air conditioning system.
  • Producing strange smells or noises: An air conditioner with no issues should operate almost silently, and it should never give off a bad smell. 
  • The air conditioner is short cycling: Your air conditioner might be showing signs of malfunctioning if it has trouble starting up after it has shut itself off or if it shuts itself off more frequently than usual.
  • Increased energy bill: If your energy bill has spiked suddenly and nothing has changed, then it could be a sign there is a major issue with your air conditioner.
  • Needing frequent repairs: As long as an air conditioner is functioning properly, it should only need to be serviced once a year to keep it in tip-top shape, but if it is constantly in need of repairs, then it can quickly become more of a problem than it is worth.

Final Thoughts

Unfortunately, there is no one clear cut answer to why an air conditioner is making a whistling noise. Instead, there are many possibilities. But now you have a general understanding of how to potentially fix the issue.

Also, since we went through some additional problematic noises, you should have a very good understanding of whether you can fix the issue yourself or if you need to call a professional.