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When the weather starts heating up, your prized home possession is no longer your collection of vintage plates or that sofa you spent months tracking down—it’s your air conditioner. For anyone living in a warm climate without central air, window units are a must. But how much do you know about AC maintenance? Aside from a perfunctory spring cleaning of the filter, it’s easy to forget about upkeep. 

Turns out, there’s more to it than an annual spruce up. According to Yooshin Kim, senior engineer at LG Electronics R&D Lab, making a few tiny tweaks to your schedule is the difference between a cool, carefree summer and having to deal with repairs. Whether you just bought a spiffy new AC unit or want to do everything you can to ensure the one you already have doesn’t go on the fritz, bookmark these tips to see you through the season.

Don’t Forget that Size Matters

The first thing you need to do is make sure you’re picking the right kind of unit. Per Kim, the most common purchasing mistake is buying one with too many British thermal units (BTUs). “If it’s too big for your space, it’ll quickly lower the temperature, but it won’t properly reduce humidity orrun efficiently,” he says. Your magic number is down to the size of the room you’re trying to cool; according to Consumer Reports, the rule of thumb is 20 BTUs for each square foot. 

Use It Judiciously

While it may be a pain to have to continuously restart your AC every time you come back home, having it constantly running not only hikes up your electric bill, it also shortens your unit’s life span. Look for a model that has a remote-controlled app if you tend to forget to turn it off. 

Heed the Warning Signs

“Inefficient cooling is a telltale sign that something may not be working,” cautions Kim. The problem could be that your little machine is overexerting itself. “Make sure any gaps around and between windows are sealed so you efficiently cool the room,” says the expert. Weather strips and foam seals are great for closing up any pesky gaps.

Normalize Deep Cleaning

This means more than just in the springtime. Regular filter checks and cleaning sessions will guarantee that your AC is running efficiently. Kim recommends clearing it out every two weeks—some models have an indicator light that flares up when it’s time for a wash. Use a vacuum to get rid of loose debris and dust, before taking the netting to your bathtub or sink to give it a thorough rinse in warm, soapy water. If it needs extra attention, get rid of mold with a bleach solution; just be sure to thoroughly dry it before putting it back into the window unit. 

Oh, and don’t forget to give every part of the fixture some TLC. “Under the filter are the evaporator coils, which should be cleaned as well to eliminate airborne particles,” continues Kim. “You should also check the fins on the exterior of the unit to make sure they stay in place.” Buy a special comb to straighten out any bent ones.

Put It on a Seasonal Schedule

Realistically, not everyone will be able to uninstall and reinstall their AC when the weather changes—but if you can swing it, storing it when you gear up for colder temps can help you maintain it in the long run. “It will perform better and last longer in the summer months if you do,” says Kim. 

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