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What Happens if I Run My AC Without a Filter?

It seems like such a small oversight, but running your AC without a filter has serious long-term consequences. A variety of things, including the unit freezing over, will happen if you run your air conditioner without a filter.

While most of your air conditioning system is a mechanical mystery, there is one aspect of the air conditioner that every homeowner must deal with: Changing the filter. Your HVAC filter is a uniquely designed sheet of densely layered fiberglass or other filtering materials. It keeps everything from dust mites to mold spores out of your AC and ventilation system, and it is a surprisingly vital part of your home HVAC process.


Consequences of Not Having a Filter

You know that the filter needs to be changed monthly, and you know that your system needs a filter. But what exactly happens if you take out the old filter and do not have a new one?

Your Home Air Will Get Dusty

The simplest consequence to running your AC without a filter is that the air in your home won't be filtered anymore. Most people don't realize it, but we are breathing filtered air all the time when indoors. It's one of the reasons that there is a real difference between indoor and outdoor air quality. The filter in your HVAC system is constantly preventing dust and pollen from being cycled through the system and blowing through your vents. So without a filter, your vents will start blowing unfiltered are, full of all the dust and pollen and particles that are in the outside air. You may experience worse allergies, sinus problems, or respiratory problems as a result.

Dust Will Build Up in Your Vent Ducts

Worse, that dust blowing through your vents will build up inside your ducts, making filter-free AC a not-so-temporary decision. Your ducts are ridgy inside and are supposed to only channel filtered air. However, once dust is flowing freely through the system, it will start catching on the ridges inside your ducts and begin to build up. When this happens, even putting in a new filter may not fully repair your air quality, as that built-up dust in the ducts will have to clear over time and may never be fully clean again without service.

Dust Will Get Inside the AC Unit

But the worst consequence of all is that running your AC without a filter can damage your AC unit. Normally, air enters your AC through the filter so that the machinery inside is only exposed to filtered dust-free air. Once you're running your AC without a filter, dust can enter the unit freely and will begin to coat the inner workings of your air conditioning unit causing a surprising number of problems with unexpectedly serious consequences.

Dust Will Coat the Cooling Coils, the Coils Will Freeze Over

Air conditioning involves pumping icy coolant liquid through components while clean air is blown past them. The cold components pull heat and moisture out of the air. Because of this, the cold components (coils and fins) are wet all the time because of condensation. When dusty air blows past a wet surface, it sticks. Running your AC without a filter exposes the cold wet components inside the AC to a steady supply of dust. The dust slowly builds up on the coils and fins as it sticks, creating a thick blanketed layer of dust over your coils. The problem? Now the passing air can't reach the coils, meaning the coils can't cool the air — and the air can't warm up the coils. This can result not only in warm air and non-functional AC, but it can also lead to your coils freezing completely over as they are unable to stay warm in the moving air.

Your Condensate Drain can Clog Up

Of course, the coils aren't the only things that dust can foul up inside your AC. There are also lesser problems that may occur before your AC freezes over completely. The condensate drain, for example, is the small drain leading out of your AC unit that takes away the water that condenses on the coils and then drips into the pan at the bottom of the unit. When dust is allowed to mix with the condensate water, it can form a sludge rather than a clean trickle. This sludge is often thick enough to clog the small condensate drain partially or completely. And when this happens, water will build up inside your AC until it damages the electricals above the catch pan.

Your AC May Overheat and Fail

If the dust builds up in a way that restricts airflow into or out of your AC, this can cause a different kind of temperature problem. Rather than preventing your coolant coils from warming up, you can trap too much heat inside the AC causing it to overheat and shut down. Overheating can be even more harmful to your unit than freezing because it can fry other circuits and parts inside your AC system.

Mold Can Start Growing in the AC System

Believe it or not, that filter was also protecting you from household mold. Mold spores are always in the air. They are a natural part of any living ecosystem, meant to alight on dead wood and other natural materials and slowly break them down into soil. But mold spores inside your house will try to break down your home, furniture, and laundry into soil while releasing human-toxic spores into the air to make more mold to finish the job. Your old air filter used to keep mold spores out of the AC system and vents. But now, without it, those spores are traveling all through your home. And anywhere they find moisture in the vents or even inside your AC unit, mold can grow.

Your Power Bill Will Rise

Finally, and this may be the first thing you notice, your power bill will go up. No matter what goes wrong with leaving your AC filter-free for an extended time, it will definitely affect your power bill. If your AC can't draw air, it will try harder which will burn energy. If your coils are becoming coated in dust preventing the air from cooling, your AC will work harder to pump cold air and burn more energy. So if you see your power bill unusually high and you're running without a filter, that's the reason.

We Can Be of Service

Running your AC without a filter for one night is a bad idea, but survivable. Running without a filter for months is an almost guaranteed recipe for serious maintenance troubles in the future. Even if you get that filter back in today. So whether you've just realized that your AC hasn't had a filter the whole time since you moved in, or you just forgot to buy a new filter this month, we can help. Contact us today if you are experiencing AC problems as the result of a missing filter or if you're not sure how to replace the filter in your home. Our team will be happy to connect you with the right filter, the right installation, and repairs for any damage caused by time spend without an AC filter in your system.

Call (305) 805-8166 to ask how we can help.

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