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May 13, 2024

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    If your AC unit is making pulsating sounds, you’re probably concerned something is wrong with it. However, it doesn’t always mean it has a serious issue. Still, you should investigate any abnormal sounds to keep it running efficiently. Typically, air conditioners make pulsating sounds if the filter is clogged, the fans are unbalanced, or if the motors are straining. This guide explores the common pulsating noise causes, how to fix them, and when to call an HVAC pro for help.

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    Is a Pulsating Noise in My Air Conditioner Normal? 

    Any loud noise coming from your air conditioner at startup and when it is running — whether it’s pulsating, squealing, clanking, a humming noise, or a buzzing noise — can be a cause for alarm. 

    So, when it comes to a pulsating noise specifically, how worried should you be? The answer won’t surprise you. It could be no big deal and a quick fix, or it could be a very big deal. 

    But does that sound normal? Nope. A pulsating noise is not normal for an air conditioner and should be looked at and fixed sooner rather than later. 

    What Could Be Causing the Pulsating Noise in my Air Conditioner?

    A pulsating noise in your air conditioner or heat pump can be caused by a variety of factors, ranging from minor issues to more serious problems. Here are the most common culprits behind this annoying sound.

    Plastic Outdoor Unit Pad

    If your outdoor AC unit is sitting on a plastic pad, the vibrations from the compressor can cause the pad to resonate and create a pulsating noise. Adding a sound-dampening material between the unit and the pad can help reduce this noise. Alternatively, you can have a local contractor pour a concrete pad for your air conditioner to eliminate the noise entirely.

    Air Handler Not Balanced on Basement Floor

    If your air handler is located in the basement and is not properly balanced on the floor, it can cause vibrations and a pulsating noise. Check it with a bubble level. If it is unlevel, add rubber anti-vibration pads under it to get it level.

    Dirty Air Filter

    A clogged air filter will reduce or block airflow from the blower motor. This will cause the system to strain and could lead to a pulsating noise. You should check your air filter every month and replace it when it is dirty – about every 3–6 months, depending on the type of filter.

    Blower Fan Out of Balance

    If the blower fan in your air handler (indoor unit) is out of balance, it can cause a pulsating noise as it rotates. This is often due to a buildup of dirt and debris on the fan blades or loose parts, which can throw off the balance and create vibrations down your ductwork. To clean the fan, turn off the power to the AC unit (don’t just turn your thermostat off; flip the breaker) and use a vacuum with a soft brush attachment to clean it.

    Condenser Fan Out of Balance

    Similar to the blower fan, an out-of-balance condenser fan can also cause a pulsating noise. The condenser fan is located in the outdoor unit and is responsible for releasing heat from the refrigerant. It can build up with dirt and debris over time – you can use a shop vacuum to clean it off. In some cases, the fan can get damaged from debris falling into it. If this is the cause of the pulsating noise, an HVAC technician may need to replace the fan.

    Bad Fan Motor Bearings in Condenser

    Over time, the bearings in the condenser fan motor can wear out, leading to a pulsating or humming noise. During regular HVAC maintenance, the contractor will lubricate these parts. However, if left unchecked, this can cause the motor to overheat and fail, resulting in a more costly repair.

    Low Refrigerant Levels

    If your AC system is low on refrigerant, it can cause the compressor to work harder, potentially leading to a pulsating noise. Air conditioning units are closed-loop systems, so low refrigerant levels are always caused by leaks. So, you’ll need an HVAC professional to inspect it, fix the leaks, and recharge the refrigerant.

    Dirty Condenser

    A dirty condenser (outdoor unit) can restrict airflow and cause your AC system to work harder, potentially leading to a pulsating noise. Regular maintenance, including cleaning the condenser coils of outdoor debris like leaves, twigs, dirt, grass clipping, etc., can help prevent this issue.

    Can I Fix a Pulsating Noise on my Air Conditioner, or Should I Call an HVAC Repair Pro?

    You can definitely save some money in the short run by fixing smaller problems yourself. But for bigger issues, it might take a trained HVAC technician to take care of the problem. For instance, with the refrigerant line, you might be able to take care of it yourself, but if getting into walls sounds daunting, you might want to leave it to a pro. The vibration might be causing enough friction to create a refrigerant leak, which is also a matter you should leave to the professionals.   

    Here’s a look at some common causes and potential fixes to pulsating and other air conditioner noises in your unit.

    Final Thoughts on a Pulsating Noise in Your Air Conditioning

    The good news is that a pulsating noise is often a very simple DIY fix, like tightening up a loose coil fan or fan blade or even putting some sound-reducing material between the heat pump or AC unit and the plastic pad it sits on. And even if it is something more serious, it is nothing your HVAC technician has not dealt with before. Keeping your HVAC system clean and well-maintained can go a long way in preventing these kinds of noises from happening in the first place.

    Knowledge is power – knowing that pulsating noise is annoying but easily fixable can help you manage the problem and get on to more important things!

    Frequently Asked Questions

    Can I fix a pulsating noise in my air conditioner myself?

    You can fix some causes yourself, such as a dirty air filter or clogged condenser unit. However, you should hire an HVAC technician for more complex issues like a faulty fan motor or a refrigerant leak.


    How do I know if the pulsating noise from my AC is serious?

    The pulsating noise from your air conditioing system is likely serious if you also have weird smells, poor cooling performance, low air flow, and other unusual symptoms.


    Can a pulsating noise from my air conditioner lead to more serious damage?

    Yes, even the small problems – like a dirty air filter – puts additional strain on your AC unit, which leads to more stain. This can cause a more expensive breakdown later.


    Article Update Log
    5/13/2024
    Reviewed for accuracy, cost data, industry best practices, and expert advice by Jonathon Jachura
    Editorial Contributors
    avatar for Alexis Bennett

    Alexis Bennett

    Contributor

    Alexis is a freelance writer with nearly a decade of experience covering the home services industry. She’s built considerable expertise in roofing, plumbing, and HVAC, as well as general construction and real estate matters. In her free time, Alexis enjoys coaching women’s golf. She lives in the Triad area of North Carolina.

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    photo of Jonathon Jachura

    Jonathon Jachura

    Contributor

    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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