Why is My AC Making Noise?

air conditioner making noise

Summer might be winding down, but the days are still hot. Your air conditioner has likely been working overtime for months to combat the humid Southern summer weather, so you’d probably notice right away if it started making strange noises.

The first sign that there might be something wrong with your air conditioning unit is if it is making loud and unfamiliar noises while running. To ensure that your system is running efficiently and appropriately, it’s important to take care of whatever is causing the issues immediately to prevent any further damage and get your system working again.

When an issue arises with your unit, always make sure it’s receiving power and that all of its control settings are appropriately set. This could save you significant time and money.

If your HVAC unit is making any sound you’re not used to hearing, that doesn’t necessarily mean it’s time to panic. Here are a few reasons it might be louder or more vocal than usual.

air conditioner making noise

Diagnosing Loud AC Sounds (and How to Fix Them)


If your AC unit is making a clanging noise, a sound that stops the minute you turn the system off, it’s possible there might be something — a compacted pile of leaves, a rock, a stick, or some other object — obstructing your fan. If you can easily remove the object once the system is off, do so, but wait until the fan completely stops spinning before trying. If it seems deeply embedded or like it might be unsafe for you to extricate on your own, leave the AC unit turned off and call a professional.


Several things can cause an AC unit to make a clicking sound, from a small obstruction irritating its fan up to an electrical issue from a faulty thermostat. Regardless, if the noise stops when the unit is off, it’s probably time to call a technician and have him check things out. If you can see and reach the small obstruction, turn the unit off before attempting and wait for the fan to completely stop moving before reaching in.


If your AC system sounds like it’s grinding, turn it off immediately. It’s possible that something has failed or is about to, and running a unit with parts that need replacing can do damage to other elements. Call a technician to repair the grinding sound.

Hissing ­

A hissing could be potentially harmful, as it usually means coolant is leaking from the unit. It could also be loose ductwork, but Freon gas is medium-level toxic and could be harmful to anyone else directly exposed to it. Turn the unit off and call a technician immediately.


Something may have come loose in your HVAC unit if you’re hearing a rattling, and you’ll want to call a technician to come and take a look. Odds are he’s probably heard the noise before and knows exactly where to find and fix it.


An AC system that squeaks or squeals is likely suffering from a misaligned or worn out belt. This happens over time or with changing weather, both of which create expansions, contractions, wear and tear.

Sure, you can ignore the noise and keep running the system, but a worn belt will eventually break. Leave this repair to the professionals, and remember it’s better to call the technician before the belt snaps and you’re without air conditioning.

Common Issues that Cause HVAC Noise

Compressor Issues

The compressor is the part of your system that is located outside the home.

Some of the most common reasons for strange noises are related to the outdoor unit. It’s one of the most critical parts of your HVAC by taking in cool refrigerant gas from inside your home and extracting it so that it becomes a warmer and higher pressure gas.

Any noise coming from your ac unit could be related to a problem with the compressor. It’s important to listen carefully to the kind of noise your system is making to identify the issue correctly.

A banging or clanking noise could indicate that there are broken or loose parts in the compressor such as a rod or mount. A buzzing noise coming from your air conditioner can be related to an issue involving a failing fan motor, faulty wiring, or burning at the fan contactor relay switch.

Because the compressor is one of the most vital components of your air conditioning system, it’s essential that you call a professional immediately when a problem arises and have them inspect your system to diagnose what is wrong.

Isolation Feet Issues

The isolation feet are small rubber pads inside the unit which mount the compressor. Like parts in any system, these pads get worn out after an extended period of continued use. This deterioration can result in the pads cracking and disintegrating. When this happens, the compressor becomes unbalanced which causes your unit to make a buzzing noise while it operates.

If you believe your system’s isolation feet have become damaged or worn, then it’s time to contact a technician to come and inspect them and replace them if necessary.

Freezing Issues

One of the most common problems that can cause unwanted noise from your air conditioning is when the unit becomes frozen. This can happen for many reasons.

If your air conditioning is not properly flowing air through its evaporator coil, it will be unable to collect the heat from your home which results in the temperature dropping which can lead to your air conditioner eventually freezing.

When your air conditioner becomes low on refrigerant, it can lead to low pressure inside the system which results in colder temperatures. As your system’s evaporator coil drops and eventually reaches below freezing, the air will freeze as it comes into contact with the coil and will build up ice in your unit.

Mechanical failures are also a common cause of freezing in air conditioners. If a part of your air conditioner is broken, loose, or a filter is clogged up, they can all lead to built up pressure inside the unit which will lead to freezing.

Freezing can also happen if you have your air conditioning unit running when the temperature outside is below 62 degrees since this causes the pressure in your system to drop.

If you find or believe that your air conditioner is freezing, it is vital that you shut it off immediately to prevent any further damage from taking place. Once off, you should try to thaw out your system by using hot water or waiting for the ice to melt.

If your air conditioning system is continuing to freeze even after thawing it, then it is time for you to call a technician who can inspect your unit and find the problem and make repairs as necessary.

Electrical Issues

Another common cause of noise coming from your air conditioner can be from issues related to electrical components inside of it.

Things such as your air filter filling up or having your unit in a dirty area can cause your system to run harder and less efficiently and damage components such as the motor fan and circuit breaker. If a component is damaged, you will hear a buzzing noise coming from it while it runs.

If a component in your air conditioner needs to be repaired, contact a professional technician immediately to get your system fixed and running correctly again.

air conditioner unit making noises

Issues Involving Debris

With part of your unit being outside, this leaves plenty of opportunity for dirt and other forms of debris to get into your system. When debris such as sticks gets into your air conditioner, it can stop your unit from functioning correctly by getting stuck and lodged in your condenser fan blades resulting in a banging-like noise.

Fortunately, you can fix this problem on your own without the help of a technician or by spending any money. Make sure to turn off the power to your air conditioner and then remove any sticks or other traps debris trapped in your unit.

To avoid debris getting trapped in your air conditioner in the future, take care of outdoor area surrounding your unit by picking up any trash around it and trimming any bushes or trees to prevent any litter getting in your system. You should have at least three feet of clearance all around your system.

air conditioner making noises

Duct Issues

A broken duct can cause a whistling-like noise to come from your air conditioner. This noise is caused by opening in the duct which allows air to escape resulting in a whistling sound. Not only does this cause your air conditioner to make an annoying noise, but it also decreases the energy efficiency of your system. This will make your system run harder and longer than usual which means your electric bills will be higher!

While you can seal broken duct spots by yourself, they are sometimes located in areas that are difficult to reach. In this case, you should contact a professional to ensure that the problem is taken care of safely and correctly. 

When to Call a Repair Technician

There are several simple fixes to noisy air conditioning units, many of which include removing minor debris, ensuring a fan hasn’t come loose (and tightening it if it has), checking that motors are well-lubricated, tightening loose screws, and checking your coil fan for clogs, among others. The average person can handle many of those tasks, but knowing exactly what to do in each situation can be tricky. That’s why the world has HVAC experts.

There’s no right or wrong time to call an AC repair technician. If you’re worried about your HVAC system, are unable to diagnose a problem, can’t reach the problem you’ve identified, or otherwise feel that tackling the project might be beyond your abilities, make the call. A qualified, expert technician will come to your home and have AC system backup and running smoothly (and quietly) before you know it.

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