Updated On

June 12, 2024

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    If your air conditioning unit is making a constant banging, screeching, or rattling sound, it can not only be annoying but a serious issue, too. Fortunately, there are several ways to diagnose and fix a noisy air conditioner, depending on the type of sound it’s making. For example, a squealing noise often indicates a problem with the fan motor or run capacitor, while a hissing sound could point to a refrigerant leak. By identifying the specific noise and its cause, you can take steps to resolve the issue and restore your AC units’s quiet, efficient operation.

    If you have spent too many nights this way, read through these DIY tips to identify and fix the source of your noisy air conditioner that most homeowners can do. However, if you’re looking for a trusted, industry-leading HVAC company to take care of business, fill out the form below:

    Get HVAC Estimates In Just 30 Seconds
    Then connect with local experts to get the help you need.

    What Makes Your Air Conditioner Noisy? 

    There are many parts malfunctions that can make your air conditioner sound bad, but air conditioners can be loud even when operating optimally. If your unit sounds strange and makes noise, it could be: 

    • A bad run capacitor
    • A failing fan motor
    • A refrigerant leak
    • Bent fan blades
    • A bad air compressor
    • A bad blower 
    • A clogged, dirty, or missing air filter
    • Dirty condenser coils 

    Those are just the most common causes of air conditioner noise. There are some less common causes, as well. Diagnosing the source can be challenging, but it is well worth your effort.

    Related: Why is My AC Making a Loud Noise When Starting or Shutting Off?

    What Do Common Air Conditioner Sounds Indicate?

    The way your air conditioner sounds can help you identify the problem. There are some of these problems that are more easily identifiable than others. Here is a list of the most common sounds your air conditioner may make. 

    Squeaking or Squealing Noise

    When you hear a squealing sound from your outside unit, it may indicate that you need to replace the run capacitor, or there could be something preventing the fan from turning on. 

    If your condenser fan is off-center or one of the fan blades is bent, it can also make a squeaking noise.

    Buzzing and Rattling

    Electrical breakdowns can cause buzzing noises. There are several parts in both the outdoor unit and inside the unit that may buzz if there is a voltage problem. 

    Buzzing and rattling can also indicate that there are loose screws. When your air conditioner is running, your HVAC system‘s vibration can loosen parts and cause them to make noises that you did not hear before. 

    Banging Noise

    Sometimes, central air conditioners make a loud banging or slamming sound when they shut off. The sound can be the result of airflow and pressure in the ductwork, causing the air damper to slam shut when your system powers down.

    A loose air filter hitting the return grille, a loose fan blade in the air handler, debris in the outdoor unit, and loose parts hitting each other can all cause loud slamming sounds. 

    Pulsating Sounds

    Pulsating, thumping, or humming noises are often signs of a compressor issue. This could be due to a failing compressor, loose mounting bolts, or a problem with the compressor’s internal components. If you hear this type of noise, it’s best to call an HVAC professional for an inspection.

    Hissing Noises

    A hissing noise typically points to a refrigerant leak in your AC system. As the refrigerant escapes through a small hole or crack, it creates a hissing sound. This is a serious issue that requires immediate attention from a licensed HVAC technician to locate and repair the leak, as well as recharge your system with the proper amount of refrigerant.

    Bubbling Sounds

    If you hear a bubbling noise coming from your AC unit, it could mean that there is standing water in your condensate drip pan. This can happen if the drain line gets clogged — the water will back up and make a gurgling sound. To fix this, you’ll need to clear the drain line and ensure proper drainage.

    How Do You Troubleshoot AC Noise?

    The best way to troubleshoot your air conditioner is to perform maintenance tasks that should help extend your system’s life anyway. So, grab some air conditioning repair tools and follow these steps to remedy your AC banging, slamming, buzzing, squealing, or rattling noise. 

    Replace Your Air Filters

    Air filters are an important part of your HVAC system. Not only do filters remove dust and other dangerous particles from your home. They also protect key air conditioner components like your blower motor and evaporator coil from buildup that can cause your system to break down prematurely. 

    If you run your air conditioning system with a filthy filter, it can obstruct airflow and cause your system to freeze or overheat. A clean air filter is so vital that most AC repair technicians change it before they start checking over the rest of your system. 

    You can look into HVAC home warranty plans that offer coverage for AC repair costs or the replacement of faulty AC parts.

    Clean Your Coils

    There is a condenser coil in your outside air conditioning unit and an evaporator coil in the indoor air handler. While a dirty coil usually doesn’t make any noise, it can cause other parts to fail. 

    If sticks or other debris are in the outside unit, the fan may make a strange sound as the blade spins. Before you clean your coils, you should shut the power off to your air conditioner. 

    There should be a switch net next to your outside air conditioner unit, as well. You should always turn the power off at the switch to ensure that your air condenser does not turn on while you are working on it. 

    Once the power is off, remove any weeds or leaves around the machine. Then, carefully unscrew the top grille.

    With the grille removed, clean out anything that is around the outdoor fan. After you have all of the debris removed, use an AC coil cleaner to remove the buildup. 

    Once you clean your coil, use a fin comb to straighten any bent fins and let them dry completely before using your system.  

    For more information on cleaning your air conditioner coils, check out this video:

    Check For Loose Parts 

    You can check your air conditioner or heat pump for loose parts. It should be fairly straightforward to locate loose parts. 

    Follow the sound to locate the loose parts. Then, tighten any bolts, nuts, or screws that are loose. 

    Check For Refrigerant Leaks

    Refrigerant escaping your system often makes a hissing sound. You do not have the tools necessary to check your refrigerant levels. 

    You can check for ice on the condenser unit and refrigerant lines. and evaporator coil. If your system is low on coolant, you will likely see ice on your air conditioner. 

    If you see frost on your air conditioner, you will need to contact an HVAC technician to check for leaks and perform a tune-up.

    Final Advice On How To Fix A Noisy Air Conditioner

    There are many air conditioning problems you can fix on your own, but hiring a professional air conditioner repair technician gives you peace of mind. Fill out the form below to get quotes from some of the top AC brands:

    Get HVAC Estimates In Just 30 Seconds
    Then connect with local experts to get the help you need.

    Frequently Asked Questions

    What does it mean when my AC unit makes a clicking noise?

    A failing thermostat, a problem with the compressor’s electrical components, or loose parts in your AC unit can all make clicking sounds.

    Why is my AC unit making a whistling noise?

    Whistling sounds are usually due to an airflow issue — a clogged air filter, blocked vents, or a damaged duct.

    My air conditioner is making a screeching noise when it starts up. What could be wrong?

    A screeching noise at startup usually points to a failing compressor or a problem with the compressor’s motor, such as a worn-out belt, dry ball bearings, or other worn out parts.

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    Reviewed for accuracy, cost data, industry best practices, and expert advice by Jonathon Jachura.
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    avatar for Jonathon Jachura

    Jonathon Jachura


    Jonathon Jachura is a two-time homeowner with hands-on experience with HVAC, gutters, plumbing, lawn care, pest control, and other aspects of owning a home. He is passionate about home maintenance and finding the best services. His main goal is to educate others with crisp, concise descriptions that any homeowner can use. Jon uses his strong technical background to create engaging, easy-to-read, and informative guides. He does most of his home and lawn projects himself but hires professional companies for the “big things.” He knows what goes into finding the best service providers and contractors. Jon studied mechanical engineering at Purdue University in Indiana and worked in the HVAC industry for 12 years. Between his various home improvement projects, he enjoys the outdoors, a good cup of coffee, and spending time with his family.

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    Roxanne Downer


    Roxanne Downer is a commerce editor at Today’s Homeowner, where she tackles everything from foundation repair to solar panel installation. She brings more than 15 years of writing and editing experience to bear in her meticulous approach to ensuring accurate, up-to-date, and engaging content. She’s previously edited for outlets including MSN, Architectural Digest, and Better Homes & Gardens. An alumna of the University of Pennsylvania, Roxanne is now an Oklahoma homeowner, DIY enthusiast, and the proud parent of a playful pug.

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