Imagine escaping the scorching summer heat, only to come to your air-conditioned home and find out that it smells musty. There aren’t many things more upsetting than that. But then, once you get a whiff of that horrible smell, you must do something quickly.

How can an air conditioner smell so awfully? Isn’t the air from an AC supposed to be odorless? Does this imply more savings wasted? It feels even worse if you have just purchased the AC unit, and it has already managed to turn your room into an unpleasant place.

Many might think they were sold a dysfunctional air conditioning system and want to return it to the store immediately to get a refund. However, one shouldn’t have to go down this road as it is unlikely to solve the problem at hand, which begs the question: why is it that my new air conditioner smells musty?

A musty smell from AC is caused by a build-up of bacteria that forms in the drip pan or drain line, on the evaporator coil, or the drain of your cooling system. As the evaporator coil is pitch-black and damp, different kinds of mildew and mold tend to grow in the region, causing a nasty smell.

Hence, if you notice your new air conditioner emitting a musty odor after regulating the thermostat to a cooler setting, you should call a professional HVAC company like Clover Services to have a look. They will take it up from there and assist you in fixing the smelly AC as soon as possible.

That said, you must be wondering why a new AC unit is even releasing such a horrible smell when it should probably be odorless. There are several reasons why your new air conditioner smells musty, and we will touch on some of them here:

Excess Moisture in Air Ducts or Vents

When the humidity level is high, or there is a drainage leak that is not quickly spotted, excess moisture may build up inside air ducts and vents. So, if you start to experience a bad smell after switching on your AC unit, mold has probably grown within the ductwork.

Mold exposure is unhealthy for humans as it can lead to upper respiratory problems. Hence, you should employ the services of a professional HVAC technician to have the ducts and vents of your air conditioner cleaned immediately. Once this is complete, the air from your AC should be odorless again.

Frozen Evaporator Coils

Air conditioners function by absorbing warm indoor air, ridding it of humidity, cooling it, and bringing it back indoors through return vents. Since free-flowing air is essential for this process, air filters must remain clean.

However, the accumulation of dirt and debris may disrupt airflow through air filters, which in turn causes water drops from humid indoor air to form on the evaporator coils. As the air conditioner’s refrigerant cools the air, the water drops on the coils begin to freeze, causing a musty smell from AC. To prevent this occurrence, make sure to change or clean up your air filters regularly.

Blocked Condenser Line

The condenser line, a little PVC pipe located beside the condenser unit, is that part of the air conditioner found outside your home. It drains water from the drip pan of your AC unit. This small pipe is one of the spots where mold, sludge, and mildew love to grow. The build-up of these often leads to clogs and musty odors outside your house.

This musty smell from the AC unit can be prevented by cleaning the condenser line regularly – once a month will suffice. That said, you cannot just get to cleaning immediately. First, you should switch off your air conditioner at the breaker panel and thermostat. After this, you can detach the condenser line from its attachment and pour some distilled vinegar into the aperture. Allow it to stay for about 30 minutes before ridding it of impurities with water. After the entire process, you can reattach it to the AC unit and switch it on again.

Wrong AC Unit Size

Some people fail to purchase the right air conditioning unit size for their homes and deal with some malfunction as a result. If your AC unit is too big, it will cycle air around the house too fast, so it does not get dehumidified, leading up to excess moisture. Also, a wrong AC unit size may be prone to switching on and off voluntarily, causing wear and tear of the system or even complete failure.

If your new air conditioner smells musty, contact an HVAC technician to access your unit to check if it is the correct size. Determining the correct size requires taking a lot of factors into consideration, including your home’s expanse, the number of people in it, the ceiling height, your local climate, and your insulation type.

A Full Drain Pan

When moisture is drained from humid indoor air, water droplets begin to fall into the drip pan. This drip pan is prone to wear and tear and will probably be less effective as time goes by.

Musty smell from AC units can be perceived in your homes when mold and mildew grow on an inefficient drip pan. Have a professional HVAC technician take care of the problem by replacing the pan with a new one.

These are some of the reasons why your new air conditioner might be smelling funky and causing chaos in your home. Once you notice any musty smell from your AC, you should act fast to identify the problem before fixing it. Also, make sure to schedule routine maintenance of your air conditioning unit to keep it in good shape.

Indeed, we want our air-conditioned homes to be as pleasant as possible unless you want to sit on the deck and get tanned. Hence, it is paramount to do our part to enjoy these AC units to the maximum.

Aiden Anderson
Author

Aiden Anderson earned his Master’s in Environmental Engineering from the University of California, Davis, focusing his 20-year career on HVAC innovation and indoor air quality. Since joining our platform as a freelancer in 2020, Aiden provides insights into climate control solutions, eco-friendly technologies, and system optimization. His background includes roles in environmental impact assessment and HVAC system design. His prior roles include engineering positions inmanufacturing and energy consulting. In his leisure time, Aiden enjoys woodworking and volunteering in community energy awareness programs.

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