How to Clean a Window Air Conditioner, Including Units With Mold

If you've found your window air conditioner isn't cooling as well as it once did or it's producing a mildew odor, it might be time to give your unit a thorough cleaning.

Regularly cleaning your window AC has many benefits. A thorough cleaning can improve your unit's cooling and energy efficiency, ensure that it filters out more allergens in the air, eliminate off-putting odors, increase its lifespan with less need for repairs, and prevent mold growth.

I've tested and reviewed window air conditioners for three years for our guide to the best window ACs. For this article, I talked to two HVAC contractors: Ray Bramble, owner of Aire Serv of Bull Run and Aire Serv of Central Shenandoah Valley, and Vincent Drago, owner of Mini King in Westchester County, New York.

Quick tip: Check your air conditioner's user manual for the most accurate and relevant cleaning tips. Most user manuals can be found on the manufacturer's website.

You should clean your window air conditioner thoroughly at least once a year. The best time to clean is right before you install it for the season or right after you remove it since you can easily take the unit apart.

Before you clean the AC, you should always turn it off and unplug it. If you can't unplug it, turn off the circuit breaker to the unit.

You will need the following materials:

How often: When the "clean filter" light illuminates on the control panel or about once a month

To clean the filter, open the front grill of your air conditioner and pull out the filter. Shake the filter outdoors or use a handheld vacuum to remove the debris. Then wash the filter with warm water and soap. Allow it to dry completely before reinstalling it.

How often: Annually or as needed

Quick tip: Know the difference between coils and fins. Coils are the approximately quarter-inch pipes that contain the refrigerant. Fins are sharp slivers of metal surrounding the coils. They help with airflow and keep debris off the coil. Fins bend easily, affecting their performance. Avoid touching them with your hands.

Cleaning the coils and fins is part of deep cleaning your air conditioner. Both Drago and Bramble recommend cleaning your air conditioner outdoors because it can get messy.

Window air conditioners have two sets of coils and fins: the condenser coils in the back and the evaporator coils in the front. Both are accessible by removing your unit's case.

Quick tip: Take photos throughout the process of disassembling your air conditioner to guide you when you put everything back together. Drago says carefully keeping track of the screws will also make the process smoother.

To remove the case, you will need a screwdriver. "Take out any screws that you see around the case, usually they're going to be more toward the bottom around the edges," said Drago. Once you've removed the necessary screws, you can remove the face/control panel of the unit and pull the case straight up.

Next, use a vacuum or compressed air to remove any surface debris. You might also use a fin comb or soft bristle brush to lightly remove debris from the fins.

For a more thorough cleaning, cover all of the electrical components with plastic and use a spray bottle with 3% hydrogen peroxide to spray down the fins and coils. Let the peroxide sit for about 10 minutes and spray it down lightly with a water hose. "Very lightly," said Bramble. "You're not trying to pressure wash this thing off at all because you can bend the fins over."

How often: Annually or as needed

Cleaning the insides is similar to how you clean the coils and fins. First, I like to use a handheld vacuum to remove as much debris as possible, especially the debris that has accumulated at the base of the air conditioner.

Next, cover all of the electrical components with plastic to keep moisture out. Then spray down the interior with hydrogen peroxide. Drago stressed cleaning the drain pain and fan blade since these are areas where mold could grow.

After letting it sit for about 10 minutes, lightly spray down the interior with your water hose. Hold the unit at an angle to allow the water and debris to drain. "Maybe spray it down one more time and get any of that hydrogen peroxide out of there," said Drago. "You don't want that sitting there and blowing back into the room."

How often: Annually

You can clean the exterior of your air conditioner with a damp cloth. For stuck-on debris, you can also use a mild detergent and a soft-bristle brush. This will work well on the case's exterior as well as the side curtains.

Drago recommended a deep clean of your window AC unit if you discover mold, performing all of the steps outlined above. He noted that the fan blade and drip pan are common places where mold forms.

Drago stressed the importance of using hydrogen peroxide 3% to scrub the interior clean. "That should kill most things," he said.

The safest way to thoroughly clean your window air conditioner is to remove it from the window, but that's not always possible. Fortunately, there are some cleaning tasks you can do with the AC installed.

You can clean the front evaporator coils by removing the filter and front grill of your window AC. Use compressed air to blow dust and debris from the fins. A soft bristle brush or fin comb will also work as long as you are gentle and don't bend the fins.

If you're able to access the AC from the outside, like, for example, if it's installed on the first floor of a building, then you can clean the condenser coil. You can use the dry method described above or clean with water using a spray bottle or hose with a nozzle attachment. If you use water, make sure there is no power running to the AC and that the water will drain outside. If your AC is angled correctly, the water should drain outside.

Before you reassemble your air conditioner, make sure it has dried, especially the filter. First, remove any plastic you may have used to cover the electrical components. Then fit the case back onto the unit. Loosely screw in all of the screws. Once all of the screws are in place, then you can tighten them. Lastly, you can reinstall the face/control panel and the filter.

Cleaning your window air conditioner will extend its lifespan, ensure it functions properly, and save you money in energy costs. It may be a pain the first time you do it, but it will get easier the more familiar you become with the process. Keep in mind: An hour of effort will give you a summer of coolness.

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