How to Clean a Window Air Conditioner

Photo: Lollie Weeks

Do you rely on window air conditioning units to keep things cool? Have you taken a peek inside that window AC unit's vent—the one where all that nice cool air is flowing out from? I did, and I was horrified.

Sure, a builder today wouldn't dare build a new dwelling without central air, but in older homes (like mine, built in 1904) it's not uncommon to still be sans central air. Of the 17 residences I've lived in throughout my life—from apartments to townhouses, dorm rooms to duplexes, scattered all over this fair land, from California to Missouri to New York to Massachusetts—only four of my homes have had central air. (Yes, I like older homes.)

You may be surprised to learn housing without central air is pretty common. According to the Residential Energy Consumption Survey done in 2009 by the U.S. Energy Information Administration, window or wall AC units were still being used in 58 percent of homes in the Northeast, 26 percent of homes in the Midwest, 16 percent in the South, and 27 percent in the West.

Here in our humble abode, we have several window units: small units for each bedroom, and one large unit that cools the downstairs.

Last fall, as we took the units out of the windows to store away for the winter, I took a peek inside and was horrified by the black grime that had collected in the filter and other places. Not good for a household full of allergy sufferers!

I called around for someone who cleaned and serviced wall units. No luck! In fact, one guy told me it wasn't worth the trouble and I should just go out and buy new units. But they work perfectly fine! And what about the landfills? Surely my only option wasn't tossing them all away and spending hundreds of dollars on new units!

Photo: Lollie Weeks

Over the winter, I forgot about those dirty, grimy AC units. Then spring arrived and temperatures rose, and the husband said, "I think I'll put in the air conditioners this weekend." Hold your horses honey! We've gotta do something about the filth.

Being the ever-cautious type, Chris loosely covered the electronic controls with cutplastic bags and masking tape. Then we got to cleaning.

Photo: Lollie Weeks

We slightly diluted a Simple Green all-purpose cleaner and picked up a couple of ordinary scrub brushes. First we hosed down each unit, which blasted away some of the filth, then we sprayed Simple Green on all the grimy areas. We gave the Simple Green a few minutes to do its job, then gently scrubbed every part we could reach, before thoroughly hosing down the unit.

By mid afternoon, all four window air conditioning units were fresh and clean!​

We left them out in direct sun for a several hours to make sure they were fully dry before we installed them, plugged them in, and turned them on.​

Sometimes DIY projects aren't glamorous, but that evening, when we turned on the AC units, they hummed, instead of the dull roar and rattling they had been doing before. We swear they cooled better, too!