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This article is very close to my heart, because I have personally spent many countless hours working with HVAC contractors, reading articles, watching YouTube videos, testing everything, and becoming an expert on cleaning my own AC and evaporator coils, especially for smells, mold, and mildew.

This article is my master guide on my years of research, knowledge, and experience doing it for my own home and properties.

Disclaimer

With that being said, the materials and information on this website are for informational purposes only and not intended to replace a professional licensed and certified HVAC contractor. DoorLoop and all its authors and affiliates have no responsibility or liability for any of your actions. Always do your homework and get a professional opinion before doing anything yourself.

What Are AC Coils?

To start, most homeowners know that cool air comes from the air conditioning system, but they don't realize that there are two sets of coils involved in the air conditioning process. The condenser coils will dissipate the heat, and evaporator coils are there to cool the air. You'll likely have to clean both sets, and I'll explain all that a little later.

Condenser Coils

The condenser coils are located within the condenser unit, which is large and made of metal. Overall, the condenser coils will remove heat and dissipate the hot air from within the home.

In a sense, condenser coils are just metal tubes that go through aluminum fins. Refrigerant in a gas form gets compressed into those coils, which turns the gas into a hot liquid. The fins and coils dissipate whatever heat is trapped in there when the fluid moves through them. There's also an electric fan atop the condenser unit to help with the heat transfer process.

Though they don't get cold, you need clean condenser coils because they mimic a sponge that soaks up the indoor heat and moves it outdoors.

air conditioner unit

Here's a quick recap:

Condenser coils are:

  • Found outside
  • Are located within the condenser unit
  • Can often be hosed down with a pressure washer
  • Dirtied by outdoor contaminants, such as pollen, dirt, leaves, and tree fluff

Evaporator Coils

Your evaporator coils are located inside the home next to the air handler unit. Typically, the evaporator coil gets very cold because the blower air passes through the evaporator coils to send cool air throughout the house.

The evaporator coil also runs through the aluminum fins, which is similar to condenser coils. When the refrigerant goes through the condenser coils, it will shift indoors to the evaporator coil. Refrigerant liquid enters them, expanding into a gas that will cool the coils down.

dirty ac evaporator coils

Here's a quick recap:

The evaporator coils are:

  • Found in your air handler
  • Located inside the home
  • Can't be hosed down
  • Dirtied by indoor contaminants, such as animal fur, hair, and dust

When You Should Clean Your AC Coils

Air conditioning coils should be cleaned once a year. However, if you often use the unit or have a very dirty exterior (dirt, pollen, and leaves), you may have to clean AC coils more frequently. Generally, spring is the best time for coil cleaning, but you may also do it again during the mid-summer months.

Why Clean Them?

Cleaning the air conditioner coils is a cost-effective and simple way to improve the lifespan, durability, and efficiency of your unit. Plus, it will enhance your indoor comfort and save you money on repair costs and operating fees.

Dirty coils aren't something you should live with, and they will happen every year. Though coil cleaning takes some practice, you'll get faster and easier results the more often you do it.

Learning to handle coil cleaning yourself means improving the efficiency of your system, reducing technician calls, minimizing wear, and saving money.

Improve the Cooling Efficiency

When dirty, the components of your air conditioning system work harder to put cold air into the house.

Overall, the compressor and condenser fan work harder to output the same cold air in the home. When you clean the AC coils, you'll restore them to a decent state so that they're operating within their intended capacity!

Minimize Wear and Tear on the System

Dirty coils will make the air conditioner system cycle on and off more frequently to maintain your preferred temperature. The condenser fan unit must constantly work to draw the hot air out of the house, which causes it to wear out much faster.

Reduce Service Calls

You will have more complex and larger repairs as your air conditioner ages. In those cases, you'll likely need to hire an HVAC technician and pay for a service call.

Generally, service calls aren't cheap and can range from $100 to $200, which is only for them to show up and diagnose the problem. You'll also have to pay for materials, labor, and more. I recommend coil cleaning to reduce the number of calls you must make to a professional.

Safety Considerations

Using coil cleaner products can be dangerous. Therefore, when cleaning the air conditioner, it's wise to use chemical-resistant clothes, chemical-resistant gloves, a face shield, and safety glasses.

Though the air conditioner unit itself will be outside and have plenty of ventilation, you're focused on cleaning the evaporator coils, which are inside the home. Likewise, AC units are 240V systems, so you should fully disable the electricity before using a coil cleaner.

Air filters

This article wouldn't be complete if we didn't quickly discuss your air filters. Most people will recommend changing them once every 3 months. In my experience, once a month is the best if you can. If they are constantly getting very dirty, your AC will need to run harder to pull my air through the filter, and you will get more dirt and debris inside your coils.

After much research, including this article, I use a MERV 8 filter that gives me the perfect balance between clean air, and overloading my AC unit. The stronger and thicker the filter and filtration (like a Merv 12), the harder your AC needs to work to pull air. Your electricity bill will increase, and you may run into issues, breakdowns, and more maintenance.

Step-by-step Guide

So without further adieu, here are the steps you should take to clean your AC closet and evaporator coils. All of these links are products I personally own and use. They are not affiliate links and we do not earn any commission if you buy anything:

  1. The first step is to always turn off your electricity breaker to the AC unit. Some units will have their own breaker on the unit itself.
  2. Use a shop vac like the Armor All 2 HP Wet/Dry Vac to suck out any dust and dirt from the closet or space surrounding the unit. I have this shop vac and it's incredibly convenient, portable, and powerful.
  3. Open the bottom and top panels of the AC unit. You normally need a 1/4ÔÇ│ hex head ZIP screws for residential AC units and a 5/16ÔÇ│ hex head for commercial units. You can use any electric or manual screwdriver, or a power drill, as long as you have the correct drivers. I personally purchased these and they work great.
  4. Using a dampened cloth or microfiber towel and wipe down the sides of the coils, making sure not to get any lint or debris on the coils. You can also grab some moist paper towels for this step. WARNING: Do NOT press hard when you clean the AC coils, or you can bend the fins which make it less efficient. Don't worry if you bend a few, just make sure to touch them as little as possible.
  5. Wipe down everything in the AC unit and the closet, removing as much dust as possible. It's wise to use a non-toxic cleaner, such as Meyer's All-Purpose Cleaner Spray.
  6. Remove any large debris from the coils, such as hair. Sometimes, a lint roller can be a great tool to reach the back and eliminate more dirt.
  7. I used this special Air Conditioner Condenser Brush to clean both the bottom and top of each evaporator coil. It didn't work wonders, but it helped a bit.
  8. Grab a can of compressed air, and use it on top of your coils so that everything is pushed to the bottom. Once you've used compressed air, the debris should be removed from the space. You can also use an electric air duster, blowdryer (on cold), or any blower. This didn't help me that much, but mine wasn't that dirty.
  9. You can use that same air duster for the blower and any place else you like. I recommend holding the air duster in one hand while the shop vac is in the other to suck out the dust blowing around you. It's wise to use a shop vacuum with a HEPA filter inside because you don't want all that debris pushed back into the house.
  10. Use a Coil Cleaner Foam like the Frost King ACF19 Foam Coil Cleaner or Nu-Calgon on your bottom coils first. It's possible I had a bad bottle of Nu-Calgon, but the Frost King worked MUCH better for me and foamed up a lot more. I strongly recommend wearing an N95 mask and goggles for this because the coil cleaner contains chemicals you don't want smelling, and you're in big trouble if it gets in your eyes. Ultimately, it will be dark in there, so a flashlight or headlamp is crucial.
  11. Next, you will use the AC coil cleaner foam at the top of your coils if you can reach them. In "A-Frame coils", you should be able to reach them.
  12. If you wish, you can fill a spray bottle with water and spray it down completely, but it's not required.
  13. I recommend using a Bissell Steamshot Deluxe Steam Cleaner on every coil and the surrounding areas (including metal pipes). This will thoroughly clean everything. Also, it will work on those hard-to-reach spots underneath your coils. The cleaner works incredibly easy, but it does take some time to build the steam after a few seconds of usage, so it takes some time, but works well!
  14. Use your steam cleaner to blow some air into your bottom drip pan if you notice any yucky stuff stuck down there.
  15. Next, I recommend you use your shop vac to get rid of anything else that might be left in that drip pan.
  16. Flush out the drip pan with some Heinz Distilled White Vinegar. Wait about 20 minutes before flushing it out with some warm (not hot) water.
  17. Grab a fan or two to thoroughly dry everything inside the space UNLESS you're going to use a fogger later (see below).
  18. While things are drying out, grab a long hose and flush out the condensate drain line to remove blockages. This should be a PVC pipe. Turn on the water, but bend your hose so that nothing comes out of the other end. Then, you can slowly unbend it as it goes into the pipe, fully extending it to flush out all the gross stuff. If necessary, you may clean the condensate drain pipe with a special brush that worked very well for me.
  19. Use the shop vac to suck everything from the drain pipe inside the home, too. I recommend that you put a piece of cardboard, tray, bucket, or something else under the outside drip line so that it will cover the ground. That means you're not sucking the dirt into your drain pipe!
  20. Pour about 1 cup of Clorox Bleach or Heinz Distilled White Vinegar down each pipe. If they're very clogged, you can use Drano.
  21. Add three of the Condensate Pan Tablets to your drip pan, but put them far away from your drain pipe. That will clean the area in the future.
  22. If you really want to go all-out, insert a 100W Germicidal UV-C lamp under your AC coils for about 60 minutes to help kill off the bacteria. You can move it to the other parts of your air conditioner closet if necessary. I own this exact model and use it annually in certain parts of my home. I also recommend that you install a UVC bulb in your air handler unit so light shines on your blower and/or evaporator coils. Mold and microorganisms need humidity and darkness to grow, but UVC will kill it immediately.
  23. Check the outdoor unit to see if the condenser coils are dirty. You'll want clean condenser coils after doing all that work inside. You can't use compressed air because it's a large job, but you can utilize a leaf blower and the same coil foam cleaner for the condenser coil. However, it will take about one to two bottles. Rinse everything with a water hose.

Using a Fogger

This last step was probably the most important for me in killing all bacteria, and removing all mildewy smells and odors (like Dirty Sock Syndrome odors). When you use a fogger, it penetrates every single crack or crevice you would never be able to get to.

You want to get a ULV cold fogger. ULV stands for ultra-low volume which only sprays a light mist into the air.

Which fogger to purchase?

  • I purchased this fogger. While it did the job, it left everything VERY wet, so I needed to use an air mover and leaf blower to drive everything, including the walls. While you could just let it air-dry for a few hours, this did the job in a few minutes.
  • The Fogcraft Fogger seems like it might work better. Either way, make sure you can return it.
  • EC3 from Microbalance sells their own fogger, but personally I think it's overkill if you're not doing this often. Plus, they are overpriced and you can find knockoffs on Amazon like the JMG 5L ULV Fogger.
  • Concrobium also sells their own fogger.

What solution to put in the fogger?

  • You can use any disinfectant, odor removal, or mold removal solution inside the foggeer.
  • EC3 Mold Solution is a very popular option.
  • I personally used the Concrobium Mold Control product because I didn't need to dilute it. It worked EXTREMELY well in my own home, killing all bacteria, and removing all mildewy smells and odors (like Dirty Sock Syndrome odors).

How to use a fogger?

Now that you have both your fogger machine and the cleaning solution, the process is very easy:

  1. Put the cleaning solution inside your fogger machine. Test it first outside so you know how to operate it. If there is a nozzle to adjust the flow of fog, start at the lowest setting.
  2. Turn on your breaker so the AC turns on.
  3. Once the AC starts, only turn on your fan while disabling the cooling or heating from the AC.
  4. Spray around your AC unit and lightly on your floors, ceiling, and walls to sanitize everything and add a protective cover. Spray your fogger from a good distance to avoid anything getting wet. Spray it in quick strokes, so you don't focus on one area for more than 1-2 seconds, or it might get soaked.
  5. Spray it on the bottom and top of the metal pipes, coils, and in the blower so that it will soak into your air ducts.
  6. Put the fogger under the coils or near the blower for a few minutes to blow directly into your air ducts so it will also sanitize and clean your air ducts throughout your unit. The larger the home, the longer you can keep it. I left mine running for only about 3-5 minutes, and it did a great job.
  7. Leave your fan on for about 1-2 hours to completely dry everything. Consider bringing in portable fans, as well. If your walls are wet, make sure you wipe them dry and let them air dry for a while.
  8. Close everything up and turn cooling or heating back on.

Fixing a Mildew or Musty Smell

If you followed the steps above to have a clean air conditioner, you should have a clean evaporator and condenser coil. However, if you still have a musty or mildewy smell, follow these additional steps:

  1. Use an ozone generator under the air conditioning unit when no one is at home (including your pets), running it for as long as you can to remove the odor. Turn your fan on in your AC unit so the ozone can blow inside the ducts and throughout the space.
  2. IMPORTANT: Ozone can harm or kill animals and even humans if exposed for too long. Do NOT stay inside when it's running. Once it stops running, let the space air out for 30 minutes before entering, and then open the doors and windows to get fresh air.
  3. Wipe down every surface, or consider fogging the area with some OdoBan.
  4. Use a special Hydroxyl Generator if you have a really bad issue.
  5. Add Arm & Hammer baking soda or some odor eliminator tubs inside your AC closet or other parts of your space.
  6. If the problem persists, you likely need to find and fix the root cause of the issue which can be a larger mold issue (like inside walls, floors, attics, or crawl spaces), a dead animal inside your walls, or anything else.

Mold In Air Ducts

If you followed the steps for the condenser coil and evaporator coil of your air conditioner and feel you might have mold in the air ducts, follow these steps:

  1. Purchase an endoscope camera and put it in the vents to check for mold. Normally, you will find mold at the very end of the duct, where your ceiling vent is (near the fiberglass protector).
  2. You can use the Concrobium Mold Control spray to clean the vent and surrounding areas, and even use the fogger inside the air duct. Be very careful not to clean the ducts too hard, especially if they are flex ducts, or you can damage them.
  3. If you want to go the extra mile, you can purchase Fiberlock IAQ 8000 Antimicrobial paint and paint the end of your air duct where the fiberglass insulation and the vent is. You can search Google for "Encapsulate air duct" and you will find tons of videos.
  4. If you want a professional, hire your local Stanley Steemer cleaners, or other NADCA-certified companies.

Disinfecting your space

As a last and final bonus tip, you can also use the fogger, or an Electrostatic Sprayer, to sanitize and disinfect your entire home or space. Professionals use these machines to disinfect homes, businesses, schools, hospitals, and anywhere you can image. You can use any disinfectant like this Purell one inside the fogger or sprayer. And since a product like Purell is safe and non-toxic, you don't need to wear a mask, gloves, goggles, or a Tyvek Hazmat Suit, unless you want to look cool.

Have Clean AC Coils in Your Home Today

It's possible to handle AC coil cleaning yourself! You don't have to call an HVAC professional if you follow the steps above and purchase the right products. I've even provided links to my favorite items, which should help you in your journey! Happy coil cleaning!

P.S. As a disclaimer, the materials and information on this website are for informational purposes only and not intended to replace a professional licensed and certified HVAC contractor. DoorLoop and all its authors and affiliates have no responsibility or liability for any of your actions taken from our articles. Always do your homework and get a professional opinion before doing anything yourself.

David is the co-founder & CMO of DoorLoop, a best-selling author, legal CLE speaker, and real estate investor. When he's not hanging with his three children, he's writing articles here!

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