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It may seem hard to believe, but warm summer weather is just a few weeks away. Your A/C system has been sitting unused for months, and this can often cause it to grow dangerous mold. Luckily, just a few minutes of routine maintenance could be the difference between you and your passengers getting sick or staying healthy. Best of all, you can do a lot of A/C maintenance yourself with less than $100 in parts and tools.

  • Change cabin air filter
  • Check for plugged drain
  • Disinfect entire system
  • Top-off freon

First up is the air cabin filter. This is a paper filter that stops large particulates, such as dust, in your intake from getting into your HVAC system. When it wears out, you can get dust in your car. But as importantly, mold could conceivably build up on this filter and get you sick.

Some automakers recommend you replace the cabin air filter every 15,000 miles. That might seem often, and the proper interval depends on how much contamination it has to soak up. So if you live in a dusty place, it won’t last as long. Luckily, it is usually located right behind your glovebox, engineered to replace quickly, and new ones are cheap. You can get them for $10 for many makes and models.

Second of all: your air conditioner evaporator drain tube. You know how your car often drips some water–probably onto the ground from under the front passenger’s feet–after you shut it off on a hot day? This is humidity from the outside air that condenses as the evaporator cools that air, and it’s supposed to drain out. The problem comes when the rubber tube to drain it gets clogged up. That water can build up and grow mold.

Woman pinches her nose because the interior of her car smells like lettuce after A/C mold
Smelly car interior | Andrey Popov

To start with, just look for that familiar drip from the evaporator. If you don’t see it after the A/C has been running, you can slide under the car and look for the end of a rubber tube clogged with mud or dirt. If you can’t find said tube, or can’t see an obvious clog, you might need a professional to help.

Third on our list is a full system disinfection. I know, that sounds complicated and time intensive. It’s not. You will need to buy a special cleaning spray: an automotive A/C and/or duct cleaner. Depending on the brand, you’ll see it go from $7 to $15 a can. But you won’t need all of it this season.

Simply turn on your car and run your HVAC fan on a low speed. Make sure your A/C is switched on. Then find the “plenum” or the air intake. This is not to be confused with the engine air intake. In fact, it is probably between the engine and windshield, and you might have the best access to it with the hood up. Simply spray the cleaner into this intake and let it work its magic. If you want to go crazy, you can even swap to the “heat” setting and spray it again to clear those ducts. You can see how to do this yourself in the video embedded below.

Green mold flows out of the HVAC vents because of a dirty A/C system
Moldy air conditioning | Humonia

It’s critical you keep mold forming in your car’s HVAC system. The CDC warns that breathing this mold can cause irritation, coughing, and even eventually diseases such as pneumonia.

The fourth and final item on our A/C maintenance list is not so much health-related. But it is comfort-related. As your car ages, the freon refrigerant leaks out of your A/C system. But for about $50 you can buy a can of “A/C recharge” which contains more refrigerant. It is pressurized and comes with a special hose to connect to your A/C lines. Topping off the refrigerant is definitely a task you can accomplish yourself, but you’ll want to find a video with specific directions for your make/model.

Next, find out whether you need to adjust your tire pressure for a summer road trip, or see how to fix musty A/C systems for yourself in the video below:

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