Updated On

November 9, 2023

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    It is highly disappointing when you purchase a new air conditioner only to have a funny smell enter your home. Some smells might point to major issues like an electrical malfunction or gas leak. 

    Others are less concerning, but over time they can affect your health and the life of your unit. So, it is crucial to pay attention to AC smells that are out of the ordinary. 

    Keep reading to find out what could be causing the smell coming from your air conditioner.

    When Should A Bad Smell Produce By Your New Air Conditioner Concern You? 

    New air conditioners often have funny smells. So, how do you know when an odor coming from your AC should concern you? Here are some of the most common reasons for a strange scent when you turn on your new air conditioner. 

    Your Air Conditioner Smells Like A Dirty Sock

    If your air conditioner smells like dirty socks, it could be caused by fungus and bacteria on your evaporator coils. The smell may also be accompanied by symptoms that are referred to as “air conditioner sickness.” 

    Regardless of the age of your unit, if you notice any of the symptoms below, it may be time to take action: 

    • Dizziness
    • Headaches
    • Dry Skin
    • Respiratory Illness
    • High Blood Pressure
    • Sore Throat
    • Chest Pain
    • Difficulty Breathing

    The same bacteria that cause the foul sock smell causes air conditioner sickness. So, you should call a professional air conditioning repair company to assess the problem.

    Did You Know

    If you have not had a central air conditioner for a while, there is a possibility that one of the components in your system is moldy. Due to excessive humidity in a home without air conditioning, mold and mildew can grow quickly.

    A Moldy Smell Or Musty Scent

    If you have not had a central air conditioner for a while, there is a possibility that one of the components in your system is moldy. Due to excessive humidity in a home without air conditioning, mold and mildew can grow quickly.

    You may find mold or mildew in the air ducts, too. When the air ducts become filled with unhealthy mold and mildew, it can come out when you turn on your new unit.  

    So, if you think you think your unit is moldy, you need to address it promptly. Cleaning your unit may resolve the issue, but you might also need the assistance of a professional HVAC cleaning service. 

    A Fishy Smell

    Wiring issues can cause a strange fishy smell. It is a mildly offensive smell so that may go unnoticed at first. 

    If you smell something like this, you should shut the unit off and call an electrician or HVAC repair contractor. If you are running a portable or window unit, they pull a lot of power and when you leave them running continuously, the heat can melt the wiring, circuit boards, and outlets.

    Burning or melting wiring causes the smell, and if you live in an older home, your electrical system may not be able to power your new system. 

    Sometimes, air conditioning repair professionals miss wiring problems, as they are not trained electricians. So, if an air conditioner repair technician tells you there is nothing wrong with your air conditioner, it might be time to call an electrician. 

    If there are any electrical components that need to be replaced. You should also be mindful when you plug and unplug a portable air conditioner or window unit in. 

    If you cause the outlet to loosen, the wires can touch causing them to spark, which could short your device or cause a house fire. Do not get surprised if your HVAC technician tells you that you need an electrician. 

    A Burning Smell

    If you smell a burning odor, it is also a good idea to have your air conditioner checked by a professional. However, sometimes new systems do have a funny smell. 

    It is not uncommon for heaters to give off a burning smell when you use them for the first time each year. If you smell a burning smell, you might have the thermostat set to heat instead of cool. 

    There could also be an electrical problem like an overheating fan motor. Anytime you smell something burning, you need to identify the source. If your home is on fire, go outside and call the fire department. 

    Dirty Ductwork

    Your home’s ductwork is a system of vents, an evaporator coil, condenser coil, a condensate pan, drain line, air handler, and several other essential components that make up your central air conditioning system. If any of those components are dirty, it could cause the system to produce an unpleasant smell. 

    Many homeowners use the same ductwork when they purchase a new air conditioning unit. If you have dust, debris, bacteria, and fungus growing in your air ducts, your air conditioner may smell funny. 

    A dead animal that has fallen into an air duct could cause a horrible odor to come out of your vents. Luckily, there are plenty of qualified professional duct cleaning services that can help.

    Sewage Smell

    A sewer smell could be caused by a sewer line issue. Typically, a sewer-like smell is not associated with air conditioning systems. 

    A plumber may be the correct person to call if you notice a sewage smell after turning your air conditioner on.

    If you want to get HVAC systems warranty protection, we recommend you choose from a trusted home warranty company. 

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    What Causes ‘Dirty Sock Syndrome’ and ‘Air Conditioner Sickness’?

    If your air conditioner was not used for a while, fungus and bacteria can develop in the indoor air handler, air filter, air ducts, and other parts of your air conditioner. The buildup of bacteria creates a musty smell and it can even cause you to become physically sick. 

    HVAC contractors are aware of this phenomenon because it is one of the most common reasons for a foul smell coming from your air conditioner. It is also one of the most concerning because even after you have your air conditioner professionally cleaned, you may have symptoms for some time. 

    Your indoor air quality is important because you spend the majority of your time in your home. If the quality of the air in your home is low, it can overload your immune system. 

    Your body is constantly fighting off an infection if it is left vulnerable. So, if your air conditioner smells bad, you need to take it seriously. 

    For more information on ‘dirty sock syndrome,’ take a look at this video about a couple who suffered from the condition.

    What Should You Do If Your New Air Conditioner Is Producing An Odor? 

    Any odor coming from your air conditioner that is out of the ordinary is a signal that something is not right. Due to the complex nature of HVAC systems, pinpointing the exact source of the smell might not be easy. 

    You should reach out to the HVAC service company that installed your new air conditioner. They are aware of the most and least common reasons for smells produced by air conditioners. You could also choose one of our picks for the best HVAC companies in the industry.

    By having regular tune-ups on your HVAC system, you can avoid many odors before they can affect your health or air conditioning system negatively.

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    Editorial Contributors
    avatar for Alexis Bennett

    Alexis Bennett


    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 Andrew Dunn

    Andrew Dunn

    Senior Editor

    Andrew Dunn is a veteran journalist with more than 15 years of experience reporting and editing for local and national publications, including The Charlotte Observer and Business North Carolina magazine. His work has been recognized numerous times by the N.C. Press Association and the Society of American Business Editors and Writers. He is also a former general contractor with experience with cabinetry, finish carpentry and general home improvement and repair. Andrew earned a degree in journalism from the University of North Carolina at Chapel Hill, as well as a certificate in business journalism. He lives in Charlotte, N.C.

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