Will Rain Damage A Window Air Conditioner?

Some areas have hot, humid summers and frequent summer storms. This makes air conditioning practically a necessity. Especially when rain prevents you from opening the windows for fresh air, a window air unit can be just what you need. But that might make you wonder, one rainy day, if it's safe to run your AC when it's raining. Even when it's not running - can rain damage a window air conditioner? We've checked with air conditioning technicians for the answer.
Rain does not affect your window air conditioner. It won't damage it or change the performance. The electrical components in an AC are sealed, keeping them from water damage. The only real risk to an AC is standing water, such as in a flood.
Keep reading to learn more - why you shouldn't worry about a little water in a rainstorm, and what you should worry about instead. We'll also cover the best way to check your unit for air leaks and how to seal it. Finally, we'll discuss some regular maintenance tips to keep your AC unit in great shape.
Outdoor window air conditioning units on an old New York City brick apartment building with green plants along a sidewalk, Will Rain Damage A Window Air Conditioner?

Water And Your Air Conditioner

A little rain won't damage your window unit. The pieces of the air conditioner that can't get wet are sealed and protected, eliminating any issues. But if a storm rolls through with high winds, debris can get trapped in the blower and cause problems. For this reason, it's always a good idea to inspect the unit briefly after a heavy storm. Just check it over, making sure no leaves, sticks, or other debris have gotten trapped inside.
Also, standing water is a cause for concern. If you experience flooding and your unit is left in deep water, it can ruin the unit. The electrical parts may no longer be in working order. If you're in this situation, you should have your air conditioner inspected by an HVAC technician before turning it back on once the water recedes.

How Do You Keep Rain Off Your Window AC Unit?

Since rain doesn't affect the performance of your air conditioner, there's no reason to keep the rain off. However, some people do use special covers for their window AC. This isn't really for the rain - it's primarily to keep debris out of the unit. Items like falling leaves can get stuck in the blower, which does affect your unit's performance.
If you decide to cover your AC, only use a cover designed for this purpose. Don't ever wrap the unit in a homemade cover, particularly a plastic one. Common "mistakes" are a garbage bag or a tarp. Anything that traps moisture inside the AC can cause damage. This leads to rust, mildew, and mold and can ultimately break the unit prematurely.

What Is The Best Way To Seal A Window AC Unit?

It might not hurt your window AC to have a little rain. But it hurts your window frame if rain is leaking in around a gap in a poorly framed window AC unit.

There are several ways you can fill a gap like this and keep water outside where it belongs. Even a small opening that doesn't allow water leaks still makes your AC less effective due to air leaks. For a relatively big gap, fill it in. You can use adhesive weatherstripping, like this one:

Click here to see this weather stripping on Amazon.

For tinier holes and gaps that are harder to fill, use rope caulk. It's a claylike substance, which means you can break off as much (or as little) as you need and stuff it in to fit. It's also removable - and sometimes reusable if it's still moldable and clean. Just store it in a sealed plastic bag until you need it again.

Click here to see this Frost King rope caulk on Amazon.

How Do You Insulate A Window AC Unit?

The best insulation is to install the unit properly, minimizing gaps and air leaks from the start. Be sure to follow the manufacturer's instructions for the best fit and installation, and don't forget to screw the side curtains on the AC in place. This will keep them tight and firmly in place.

But even the best work will leave some small gaps behind. You can check for these holes by first looking for spaces where light comes in. If there's a hole letting in light, it's letting in the warm air as well, making your unit less efficient. You can also identify gaps by holding a lighter up around the sides of the AC - carefully, of course. The flame will flicker wherever there is a draft, cluing you into a hole that might not be visible to the naked eye. Move the flame all around the unit's perimeter, checking the flame to see how it responds.

Once you know what holes need filling, you can follow the advice above to seal your window unit. The most effective way to plug large gaps is with adhesive weatherstripping. Rope caulk is a good choice to plug very small areas.

Do Window A/C Units Need Maintenance?

Window A/C units are a bit simpler than a whole-house system. But they aren't maintenance-free.

If the AC is used frequently, clean the filter at least once a month. If you don't turn on the AC very often, you can go a little longer between cleaning the filter. It's pretty easy to do - remove the filter and soak it in warm soapy water. Rinse everything off until it's clean, let it dry, and put it back in the AC unit.

Home air filter close up macro zoom show the dirt and particle cause bacteria inflection and sickness

Some people try to leave their AC in the window frame all year. After all, it's heavy and bulky and a pain to install. But if you live somewhere where there's an obvious "off-season" that you don't need the AC, you really should remove the unit. It lasts longer and performs better in the long run, if that helps motivate you. Just set it aside out of the way, and cover it to keep out the dust.

Yearly Maintenance Chores

There are also some maintenance issues to perform once a year or so. Make a routine of doing them before you install the unit or remove it at the end of the season. If you do it at the same time every year, it makes it a regular habit. This also helps you to remember the last time that you did maintenance on the AC.

  • Clean the fins, which can get dusty, dirty, and even grow mold if left unchecked. Mix water and a few drops of detergent in a spray bottle. Apply, then brush gently, and rinse with a hose.
  • Clean the fans in the same method. Spray with soapy water, brush gently, and rinse with a hose.
  • Check and empty the drain pan located underneath the coils. This collects condensation, and you may need to drain the dirty water. Also, check the drain hole for debris. Debris plugging the hole can cause it to back up.
  • Check for bent fins. The fins shouldn't be touching. However, it's easy to bend them. If you see any that have bent together, straighten them out. You can use a credit card, but it takes patience. Or, you can use a special tool called a fin comb.

Click here to see this fin comb on Amazon.

In Summary

There's no reason to fret over a little rain hitting your window AC. While some electrical components are sensitive to water, these have been carefully sealed. The only time that water is a real issue is in the case of flooding. If your unit is left in deep standing water, you should have it checked by a professional before turning it on again.

AC covers are not made to keep out water as much as debris. You should check your unit after big storms for leaves, sticks, and other debris that may affect the blower. It's also important to perform occasional routine maintenance, such as cleaning the filter, fins, and fans, emptying the drain pan, and straightening any fins that have bent.

If you enjoyed this article, consider reading these next:

Should Air Conditioners Be Covered In The Winter?

Window Air Conditioner Freezing Up; What Could Be Wrong?

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