5 Reasons Your Air Conditioner Smells Musty

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5 Reasons Your Air Conditioner Smells Musty

If you’ve ever walked into a room and smelled something musty, you know that it’s not a pleasant experience. It can be downright unpleasant. And if your air conditioner smells musty, that’s not a good thing. There are several reasons why your air conditioner might have this funky smell, but don’t worry – we’re here to help! Let’s take a look at five of the most common causes of musty-smelling air conditioners and what you can do about them. Keep reading to learn more!


Reason #1: Dirty Filters Grow Mildew And Lead To Frozen Evaporator Coils

Think of your air conditioner filter like a coffee filter – it’s designed to catch all the dirt and grime so it doesn’t end up in your cup. But after a few months (or sooner, if you live in a dusty area), that filter is going to be full of gunk. Depending on the type of filter you have, it’ll need to be replaced or at least washed out – and we have a guide on how often to change your air conditioner filter if you’re interested.


If you don’t change your filter regularly, though, you might start to notice that your air conditioner smells musty. That’s because moisture – whether from the air itself or from a drainage leak – can end up collecting on the filter and creating the perfect environment for mold and mildew to grow. You’ll start to smell this as air is blown through the dirty filter back out to your home. So if your air conditioner starts to smell musty, it’s time to change that filter!


Reasons #2: Dust Build-Up On The Heating Elements

The musty smell emanating from your air conditioner could be caused by a build-up of dust and dirt on the heating components. When you turn on the heat after a long hiatus, the dust will burn off, causing a burning smell. If the burning smell lingers, it might be indicative of a deeper problem with your furnace or electrical wiring. In that case, don’t hesitate to call a professional. Note: if you find that your air conditioner smells like mold, it could be due to a clogged drainage pipe. Try pouring bleach down the pipe to clear it out.



Reason #3: Dirty Or Blocked Drain Pan

The drain pan in your air conditioner is there for a very specific purpose – to catch the condensed water that is stripped from the air during the cooling process. In an ideal world, this water would flow out of the drain pan without issue, but sometimes things don’t go according to plan. If your drain pan is old or the drain line becomes clogged, you may start to see standing water. And when mold grows in the drain pan, you’ll probably notice the musty smell that accompanies it.


If you’re looking to do some DIY maintenance, you can empty and clean out your drain pan yourself. However, if you want to be sure that there’s no mold anywhere else in your system, it’s always best to get an HVAC expert to give your system a thorough assessment and cleaning. That way, you can rest assured knowing that your air conditioner is running mold-free.


Reason #4: Mold Or Mildew In The Ductwork

If you’ve ever wondered why your air conditioner smells musty, it’s because the ductwork is likely full of dust, dirt, and mold. When water pools or condensation builds inside the ductwork, it creates the perfect environment for mold to grow. The build-up of spores from the mold can then be blown down into your home by the air conditioner’s fan. This can lead to irritation and allergic reactions in people who are breathing the air in your home. That’s why it’s so important to have your ducts professionally cleaned. Not only will it improve the air quality in your home, but it will also make your air conditioner smell fresher and cooler.


Reason #5: Dirty Or Blocked Condensate Line

The part of your air conditioner that is located outside of your home is called the condenser unit, and the pipe that channels the water from inside the AC out is called the condensate line. Unfortunately, this pipe is often the source of a musty smell in your home – and it’s all because of its small size and proximity to the outdoors. The dirt, mud, and bacteria that easily clog the condensate line can quickly lead to an unpleasant odor in your air conditioner. Luckily, you can prevent this problem by cleaning your condensate line every month or two. By making sure that water can easily escape from your HVAC system, you can keep your air conditioner smelling fresh and clean.


If you have noticed musty smells coming from your AC unit, be sure to check for these common causes. Cleaning or replacing dirty filters, heating elements, and condensate lines can help eliminate the problem. If you have severe mold or mildew growth, you may need to have your ductwork professionally cleaned.



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Superior Mechanical Services, Inc. began in 1948 as a family-owned business with a vision to provide value-minded service with a down-to-earth approach to customers throughout the San Francisco Bay Area. As the premier Commercial and Residential HVAC Service provider for Livermore, Dublin, and Pleasanton, Superior Mechanical can do it all, from heating and air conditioning services to boiler services, to plumbing services. Our technicians are certified professionals who will ensure every part of your project is done right using a careful checklist to guide and test each step. At the end of your appointment, we’ll show you how to get the most out of your new system and give you tips on maintenance so it lasts for years to come. Contact us today for amazing service tomorrow!


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