AC Evaporator Coil Cleaning with Pump Sprayer and Brush

The A-frame evaporator coil front cover plate was removed to access the interior coils in How to Clean Inside of AC Evaporator Coils.

AC Evaporator Coil Inspection

The coils are 12+ years old and have never been cleaned from the inside. Overall the coils are not extremely dirty but do have some surprising mold, dust, dirt, insect bodies and debris. An important note is there is no evidence of oil on the copper coil circuits which would indicate a refrigerant leak (the HVAC service company checked my system last week and confirmed the refrigerant charge was fine). Note the air flows upward through the coils on my AC system so anything that gets past the air filter may stick to the coil faces:

AC Evaporator Coils Interior View before Cleaning

AC Evaporator Coils Interior View before Cleaning

Closeup of the right side of the coils. A fine layer of dust coats the fins with various clumps of dark stuff and what appears to be stringy pieces that may be a spider webs, pet hair or other fibers. That larger slightly silver colored object in the center turned out to be piece of HVAC metal foil tape:

Dirt and Dust Inside AC Evaporator Coils

Dirt and Dust Inside AC Evaporator Coils

View of the left side of the A-frame coils before cleaning. Note the dust line starts about 2 inches above the bottom of the coils (which are still shiny) because the plastic condensate drain pan blocks the air flow along the bottom section of the coils. The dust buildup is also greatest towards the back of the coils where the airflow is strongest directly above the blower housing outlet:

AC Evaporator Coil Cleaning - Interior Dirt

AC Evaporator Coil Cleaning – Interior Dirt

Looking down into the natural gas furnace and heat exchanger below the AC evaporator coils you can see how the drain pan (red arrow) shields the bottom of coils. The blower wheel is just visible at the yellow arrow:

AC Evaporator Coils and Gas Furnace Heat Exchanger

AC Evaporator Coils and Gas Furnace Heat Exchanger

I held the camera inside the A-frame coils to get this photo of the furnace heat exchanger, blower housing and blower wheel. The blower housing opening is located at the rear half of the furnace and begins at the two yellow lines. This is why the dirt buildup is worse towards the rear of the coils where the airflow is strongest:

Air Handler Gas Furnance Heat Exchanger and Blower Motor

Air Handler Gas Furnance Heat Exchanger and Blower Motor

My Heil natural gas furnace was made by International Comfort Products. This diagram from the Technical Support Manual illustrates the location of the blower outlet to better understand the layout:

Heil ICP Gas Furnace and Blower Motor

Heil ICP Gas Furnace and Blower Motor

AC Evaporator Coil Cleaning with Pump Sprayer and Brush

The HVAC techs clean evaporator coils with a professional grade alkaline cleaning solution and pump sprayer as explained in Heavy Duty AC Evaporator Coil Cleaning.

AC Evaporator Coil Cleaning with Nu Calgon Evap-Powr-C and Pump Sprayer

AC Evaporator Coil Cleaning with Nu Calgon Evap-Powr-C and Pump Sprayer

I’ll also use a 14 inch bench brush purchased at Home Depot that features “flagged poly fibers of this brush grab even the smallest dirt particles”. I chose this brush because the bristles are not so stiff that it will bend the coil fins if used correctly and the flagged poly fibers (i.e. really bad split ends) are like tiny fish hooks that does a great job picking off dirt. The long brush makes it easy to reach deep inside the coils. A fin straightening tool is handy for removing clumps that can’t be brushed off or fixing the fins if you accidentally dent them with the brush handle or your hand:

AC Evaporator Coil Cleaning: Bench Brush and Fin Straightening Tool

AC Evaporator Coil Cleaning: Bench Brush and Fin Straightening Tool

Spray and Clean the Evaporator Coils

The Nu-Calgon Evap-Powr-C solution is mixed and sprayed on the fins to loosen and remove the dirt. I noticed that even with a heavy thick stream the cleaning solution never shot through the coils, instead it wicked down the other side and into the condensate drain pan. Nice! But if you’re concerned about getting cleaning solution on the furnace heat exchanger or blower fan you can place towels over the heat exchanger. (Thanks to Scott A. for the towel tip!)

Cleaning AC Evaporator Coils with a Pump Sprayer

Cleaning AC Evaporator Coils with a Pump Sprayer

The large clumps of dirt/mold/whatever mostly came off with a concentrated spray. I often needed to direct the spray at a low angle across the coil face to peel off the clumps:

AC Evaporator Coil Interior Cleaning with Pump Sprayer

AC Evaporator Coil Interior Cleaning with Pump Sprayer

A sample of the debris I picked off the evaporator coils using only the pump sprayer. I think the stringy stuff is pet hair or lint. The dark globs are covered in mold. There’s even a moldy spider (gross!):

AC Evaporator Coil Cleaning - Dirt and Debris Removed from Coils

AC Evaporator Coil Cleaning – Dirt and Debris Removed from Coils

I used a full gallon of cleaning solution mixing 1 part Nu-Calgon Evap-Powr-C to 3 parts water, alternating between spraying both sides of the coils. I mixed another gallon of solution in the sprayer for the next steps to clean the coils with the bench brush.

A quick illustration of the fin straightening tool in case you need to comb out the fins. Choose the correct tool head size in threads-per-inch that match your fin spacing. I was careful and didn’t need the fin tool:

AC Evaporator Coil Cleaning - Fin Straightening Tool

AC Evaporator Coil Cleaning – Fin Straightening Tool

Cleaning Evaporator Coils with a Brush

The pump sprayer removed most of the dirt but “chunks” remained at the apex or narrow section near the top of the A-frame evaporator coils that were loose but I couldn’t wash off with the sprayer due to the narrow space. While not very apparent in this photo under bright lighting the coil fins appeared to have some caked on dust.

To clean the evaporators coils with a bench brush:

  • Have a bucket of clean water to rinse the brush.
    Best to buy a new bucket that hasn’t been used to mop the floors so there’s no residual chemicals or dirt.
  • Spray the coils with the cleaning solution.
  • Work slowly and carefully. It’s cramped and awkward work inside the coils.
  • Brush in straight lines up and down only inline with the fins.
    Never brush across the fins because you may fold and bend the fins blocking the air flow!
  • Use a light touch and brush gently, checking that you’re not bending the fins.
  • Short brush strokes are better so your movements are in a straight up & down motion.
  • Rinse the brush often in the bucket of water.
  • Spray both sides of the coils with cleaning solution again to wash off the loose dirt.
AC Evaporator Coil Interior Cleaning with Brush

AC Evaporator Coil Interior Cleaning with Brush

I’m pressing the brush downward into the fins to get at the worst of the caked-on dust where the airflow is strongest above the blower fan:

Cleaning AC Evaporator Coils with a Brush

Cleaning AC Evaporator Coils with a Brush

The brush did a really good job picking off the chunks of dirt and debris. The long bristles easily reached into the narrow top of the A-frame coils. When I took the bucket outside into the sunshine the water looked way more brown colored than this photo:

AC Evaporator Coil Cleaning - Brush and Dirt

AC Evaporator Coil Cleaning – Brush and Dirt

Here’s the A-Frame coils after cleaning and brushing with a good view of the narrow slot at the top of the coils. There’s still some brownish looking dust at the lower rear of the coils. I sprayed and brushed as hard as I thought possible without bending the fins but it wouldn’t come off. Upon closer inspection the dirt is a very fine layer that appears to be baked on the fins probably by the furnace heating during the Winter months. The spaces between the fins are clean and open for good airflow:

AC Evaporator Coils after Inside Cleaning

AC Evaporator Coils after Inside Cleaning

The Before and After cleaning and brushing the coils for comparison:

AC Evaporator Coils Before and After Cleaning

AC Evaporator Coils Before and After Cleaning

Very Dirty Evaporator Coil Cleaning

If your coils are really dirty and coated with a heavy mat of dirt then you should:

  • Soak the coils with the cleaning solution.
  • Brush off the worst of the dirt and mold, rising the brush frequently.
    Better the clumps of dirt go in the water bucket instead of the clogging the condensate drain pan.
  • Spray the coils often with cleaning solution followed by more brushing.
  • Remember to spray both sides of the coils with a heavy stream to wash out dirt between the fins.
  • Shine a flashlight through the coil fins onto a hand mirror on the opposite side to verify the air passages are open.

I finished by spraying the coils and coil case insulation with Lysol spray to kill any mold.

Reader Feedback

Don the creator of e-mailed me about his very dirty AC evaporator coils:

Hello Bob,

I am emailing in regards to AC coil cleaning. I went over your articles on that and they have helped me a lot but I have some questions I thought I would ask before I continue on with the cleaning.

Recently I noticed our AC was not draining the water like it should and it was draining from other areas of the AC especially near the bottom. I was told something has clogged up the drain pan etc. I thought I would open it up and took a look. Sure enough the drain pan does look like it can use some cleaning but then I noticed the A-Frame evaporator coils and the insides of them are very bad. The outsides are not too bad though. Below is a picture of the very dirty coil.

My question is, would a simple air condition coil foaming cleaner like the AC-Safe one from HomeDepot be helpful based on the condition of the coils in the image?

Look forward to your email! Much appreciated!
Thank you,

Dirty AC Evaporator Coils

Dirty AC Evaporator Coils

My reply to Don was an aerosol can foaming cleaner wouldn’t work because the dirt and mold has to be mechanically removed with a brush and pump sprayer using a professional grade coil cleaner. I asked Don how long it took him to clean his coils and to send a picture of the cleaned coils:

Hi Bob,

Thank you very much for your advice! Because of your very informative website on coiling cleaning and your advice, I have managed to get the coils cleaned pretty good! Below is an image of the finished work. It may look like a lot of the fins are bent, but that’s from the flash of the camera. However, there were fins that were/are bent as you can see some in the image below. I also purchased a fin repair tool and did my best in trying to straighten out much of the bent fins. Anyhow, it was the best I can do with that. It’s a pretty good furnace/air conditioner by the way.

I’ve been meaning to get back to you on this a few or so days ago. Once again, thank you very much!

It took me a good amount of cleanings. I lost count to be honest. lol. I went the extra mile on it to do my best to be as thorough as I can. I’d say hours-wise… I spent about a good 2 – 3 hours or so with breaks here and there, etc. I got it clean well in about an hour in or so but I decided to keep at it while I’m able to, etc.

Once again, thank you!

Interior AC Coil Cleaning

Interior AC Coil Cleaning

Another reader, Lauren, sent me this message and photo of her evaporator coils:

Hi Bob,

I’m a 30-year-old mother of two toddlers and my air conditioner stopped blowing cold air today. I found your website, followed the instructions, and cleaned the coils. Attached is a picture. It was disgusting! But, it’s blowing ice cold now.

Thank you for the time and effort you’ve put into your site. You saved me time and money!

AC Evaporator Coils - Interior Clogged with Dirt and Mold

AC Evaporator Coils – Interior Clogged with Dirt and Mold


The evaporator coil front cover plate is re-installed in Close and Seal the Evaporator Coil Case.

Hope this helps,

Bob Jackson

Copyright © 2016   Reproduction strictly prohibited.

26 Responses to AC Evaporator Coil Cleaning with Pump Sprayer and Brush

  1. Fermin August 24, 2014 at 9:29 am #

    Bob..I’m very grateful to YOU and people like you,who are willing to share their
    knowledge with other people…and expect nothing more than maybe a…THANK YOU
    Fermin Garcia
    San Antonio,Texas

  2. Jeff September 16, 2014 at 2:29 pm #

    Attention to Detail. Nice application of steps! And best of all taking your time to do it right. Time and money well spent.

  3. neal williams April 13, 2015 at 10:54 pm #

    Thanks bob this has been extremely helpfull

  4. Stephen June 14, 2015 at 12:02 pm #

    Thank you for taking the time to build this site! With your helpful instructions and photos, I was able to clean the outer coils and fins on my unit last night and I’m considering doing the inside now! Thanks again!

  5. Dianne July 21, 2015 at 12:02 pm #

    Thank you so much for taking time to share ,it helps so much when you are on a budget and can’t always pay for help.

  6. Scott Podojil September 6, 2015 at 12:16 pm #

    Great article, great help. I haven’t touched or really done any maintenance to my AC for around 10 years. The AC has been getting worse and worse through the years but it was subtle…bit worse every year so I could ignore it. After much struggling, I figured out how to get the a coil plate off and the insides were simply gross…hair, mold, it was icky.

    Couple hours cleaning and sanitizing and she is blowing like a champ now. I am sure I caused some damage to the unit by neglecting it for so long, but the moving parts are still moving and the house is livable if not super cold.

    Thanks for the tips!

  7. VN May 9, 2016 at 2:31 pm #

    Hi Bob,

    My coil is horizontally mounted upstream from my gas furnace, so the access door is actually at the top of the A-Frame looking down, so I can only clean the top side of the A-Frame, and not the bottom underside side.

    Is it possible (or even recommended) to cut through the sheet metal on the bottom side to get to it and clean it?

    • Bob Jackson May 9, 2016 at 8:20 pm #

      I’m not clear on your air handler / coil configuration and where the access panel would be cut on the “bottom” side. Photos would be a big help for my understanding, my e-mail is bob[at], replace the [at] with the @ symbol.

  8. Tanya May 28, 2016 at 2:32 am #

    I can’t get to the inside of my coils. I had it professionally cleaned three years ago and had my duct work replaced but the air, house smells funny.
    It’s a vacation condo in Florida and when I returned, I saw the drain pan had rusted again?
    Maybe the inside coil is dirty but I can’t get to the side of the unit only the front?

    • Bob Jackson May 28, 2016 at 10:43 am #

      What is the make and model # of air handler and evaporator coil case? Have you inspected the coils with a flashlight & mirror to determine if the interior is dirty? If you can’t remove the end plate to clean inside the coils then several exterior face coil cleanings may do the job and disinfect the coils. Drain pan tablets are required to kill algae and help to eliminate odors. Spray the interior coil case and plenum with Lysol spray to disinfect the ductwork before closing the maintenance panel.

      Rust in the drain pan is common but doesn’t cause odors. The metal drain pan may rust and/or rust stained water trickles down the coil end plates. So long as the drain pan isn’t rusted through and leaking its a cosmetic issue.

      • Tanya May 29, 2016 at 7:42 pm #

        Comfort maker.
        I have pictures to send but not sure how to send them.
        Model SFA2X2405A1

        • Bob Jackson May 29, 2016 at 7:51 pm #

          My e-mail is bob[at] replace the [at] with the @ symbol.


        • Bob Jackson May 30, 2016 at 11:51 am #

          I’m unable to find references to a Comfortmaker air conditioner model SFA2X2405A1. There may be two model numbers on the unit: one for the furnace and another for the evaporator coil case. International Comfort Products (ICP) manufactures evaporator coils for Comfortmaker. For example my Heil evaporator coil mfg label states:

          International Comfort Products Corp.
          Lewisburg, TN USA 37091
          Cased Evaporator Coil
          Model No. EED36B15B1
          Mfg. No. NEED36B15B1

          Design Pressure 300 PSIG
          Refrigerant 22

          Looking at your email photos I believe you have a slant coil similar this Goodman AWUF series air handler. See the diagram on page 6 which illustrates the slanted evaporator coil behind the air filter like yours. This style of air handler is popular for closet installations in apartments and condos.

          Your photos don’t show the entire air handler. There should be an upper maintenance panel that if opened will allow access to the back side of the coils.

          I also see from your photos water is spilling past the plastic condensate drip pan onto the bottom of the air handler. The drip pan looks clean and well drained. I think the back side of the coils may be dirty causing water to wick down the side of the evaporator coil metal frame missing the pan.

          Remember to shutoff the circuit breaker before doing any maintenance.


  9. Tanya May 29, 2016 at 7:55 pm #

    Also, someone said to clean the coils with 1 part bleach to 3 parts water, now today its bells worse now that 24 hours went by…is it due to moisture?

    • Bob Jackson May 30, 2016 at 11:55 am #

      Bleach is a disinfectant but not a detergent. Best to use the professional coil cleaning products.

  10. Tanya May 29, 2016 at 9:13 pm #

    I sent an email.
    Is it ok to spray Lysol on coils? I did and it helped but is it safe to stay in house and breath right away?

    • Bob Jackson May 30, 2016 at 11:25 am #

      A 10 second spray of Lysol is all you need. Open the windows and let the condo air out for 10 mins. Lysol is mostly alcohol and should be sprayed on the coil case insulation and plenum. There are way better cleaning products for the evaporator coils.

  11. Stacy Satterfield June 1, 2016 at 12:08 am #

    Hi Bob, I had to replace the floor under my central a/c unit, after that I cleaned the coil it was draining right, I replaced the front and back coil panels and now the water is blowing into the blower instead of draining into the drip pan to the drain line. I pulled the coil panels off and it drains right again. Am I supposed to seal the drain pan to the a/c unit to keep it from pulling air under it and sucking the water down to the blower off the coils?

    • Bob Jackson June 1, 2016 at 8:30 am #

      The evaporator coils normally sit on the condensate drip pan with no mechanical fasteners or seal. Gravity holds the coils in place. The raised rim of the drip pan shields the bottom of the coils from the air stream to prevent condensate blow-off.

      > I had to replace the floor under my central a/c unit
      Meaning you had to raise or move the air handler to replace the floor? Is it possible the coils are not seated correctly in the drip pan?

      > I pulled the coil panels off and it drains right again.
      How dirty were the coils to start with? If the coils were matted it could be the interior spaces between the fins are still clogged. The surfaces may look clean but dirt remains between the fins. If so the effective surface area of the coil is reduced causing higher than normal velocity air to be forced through the open/clean sections causing the condensate to be blown off before it can trickle down to the drip pan. (Air flows faster through constricted areas.) By removing the coil end plates the air flow bypasses the coils greatly reducing efficiency and air flow velocity; that’s why the condensate isn’t blown off and goes into the drip pan and drain.

      Remove the coil end plate and shine a flashlight through the coil onto a small handheld mirror on the opposite side. Move the flashlight and mirror over the coil surface to inspect all areas. You should be able to see clearly through if the fins are clean. If sections are clogged then that’s the problem. A small high intensity LED flashlight works great.

      You can e-mail photos to bob[at], replace the [at] with the @ symbol.


  12. Dan June 19, 2016 at 8:51 am #

    Thank you for this information. I followed the instructions but realized after trying the spray foam that it was a mch bigger problem and it needed to be cleaned from inside. When I took the front cover plate of the A coil off, the problem was obvious and it was worse than any of the puctures here. It was a solid mat of lint.

    My A coil was less accessible than most because of a furnace pipe in front of it, and all the copper lines in front of the A coil, so I had to get a little creative. I could just barely get my hand inside the A coil, and initially I was able to at least start to peel the mat away. The top of the spray can of cleaner had some plastic bristles on it, but it was too large to maneuver inside there, so I took the top off of a bottle of Shout laundry stain cleaner and screwed it to a long paint stick, so that I could reach all the way back. This stuff was stuck on pretty badly so the bristles on this were about the only thing that worked. Was able to use this makeshift tool and I don’t think it hurt the fins too badly.

    It took a few hours to get it all fished out of there, but I got it out and then gave it a couple of spray foam treatments for good measure. Got it all put back together just before midnight and was able to get a cool nights sleep.

    I would say the most irritating thing is that the contractor that put this unit in made it almost unserviceable. I had to physically cut slots into the front panel just to remove it. I also had to bend the tip of the plate on the A coil to get it out. Clearly they did not design this to be serviced and obviously it never was.

    My front cover plate is a hatchet job now but this whole thing saved me a few thousand dollars. Just in time for fathers day.


    • Bob Jackson June 19, 2016 at 11:31 am #

      Hi Dan,
      Thanks for sharing!

      My AC units are about 15 years old and only 10 SEER so I’m thinking about replacing them next year. Before buying new units I’ll review the service manual and look at the air handler to ensure the A-frame cover plate can be removed for cleaning. I also won’t buy an outdoor condenser unless it’s protected by a louvered metal shell to protect the condenser fins.

  13. Chris Power June 30, 2016 at 7:14 am #

    Wow the best post I have ever seen for cleaning the Coil and a great explanation for each step. Thank you for your time in doing this. My coil is laying horizontal and I’m sure my ac guy is only cleaning one side and not removing the plate. I’ll ask him to do that when he comes again. Again thank you for doing this

  14. Nate July 25, 2016 at 1:48 am #

    Hello. First, thanks so much for all of the info on your website. I have a question about cleaning the inside of my A-Frame coils. I have removed the panel to get access to the a-frame however when I try to pull it out, it slides out for a few inches but then gets some resistance due to the liquid and gas lines that Are connected to it I didn’t want to over force it and damage either of those lines but I can’t seem to remove the a frame front panel until I can slide it out further. Any tips on how I can access and remove the a-frame panel? Any help would be greatly appreciated since my family is not doing so well in the hot and humid heat we get in kentucky at this time of year. I have very little air flow through the vents and am positive that this is the issue. When I tried to flash a light through the a-frame, no light at all was coming through to the other side.

    • Bob Jackson July 25, 2016 at 12:45 pm #

      It seems the air conditioner manufacturers don’t design the evaporator coils for easy maintenance with all those refrigerant tubes in the way. I’ve seen some coils where the maze of tubes was so dense I doubt it would be possible to remove the end plate.

      See this comment by WMN dated June 9, 2016 that has the same problem. He wrote:

      “All the piping was going through holes in the sheet metal cover with no way to remove it. I had to very carefully Tin Snip out the cover pipe areas in order to remove it. After this. I discovered that there was no way to completely remove the front coil cover plate completely due to the design of copper piping in the way! So, I had to carefully pull it out enough to tin snip the cover plate into two pieces.”

      I recommended making an overlapping two-piece replacement end plate out of galvanized sheet metal.

      • Nate July 26, 2016 at 4:48 pm #

        Thanks so much for the reply. I was able to borrow some tin snippers and make myself an access label and finally I did remove the A-frame coil plate cover. However I have a new problem and would certainly welcome any advice. I cleaned the fins the best I could. (There was a literal carpet of pet hair/mold/gunk etc. That I removed and once I put it all back together the air flow is WAY better now. The only problem is now it seems like the air temp is not as cold as it used to be. Could I have made a mistake during reassembly? Any and all advice or comments would be greatly appreciated.

        As others have said, I am in complete awe of your willingness to help ppl out with your posts and replys and your whole website in general. Thanks.

        • Bob Jackson July 26, 2016 at 6:47 pm #

          Glad to help out!

          Did you make a replacement A-frame coil end plate and install it? If the end plate is missing air will spill out the end bypassing the coils instead of being forced through the coils. Bypass air won’t get chilled. If you did fabricate and install an end plate either:
          * The coils are still dirty – but not so bad as before! Can you shine a flashlight through the coils now?
          – or –
          * The refrigerant charge may be low and need to be topped off. If the charge is very low the coils will ice up. A moderately low charge will reduce the cooling capacity.


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