How to Clean Inside of AC Evaporator Coils

By |Last updated on |Central AC Maintenance|24 Comments

This project shows remove the front cover plate and clean inside AC evaporator coils where dust, dirt and debris accumulate on the upwind side.

This is my 12 year old coil before and after cleaning the inside:

How to Clean Inside of AC Evaporator Coils

AC Evaporator Coils Before and After Cleaning

Table of Contents

  1. How to Clean AC Evaporator Coils
    Seasonal exterior coil surface cleaning with a spray-on foam.
  2. How to Clean AC Evaporator Coils – Part 2
  3. Heavy Duty AC Evaporator Coil Cleaning
    Deep cleaning with professional coil cleaner, pump sprayer and brush.
  4. How to Clean Inside of AC Evaporator Coils (this project)
    Interior coil cleaning by removing the coil end plate, best for very dirty coils.
  5. AC Evaporator Coil Cleaning with Pump Sprayer and Brush
    Clean the coils inside and out.
  6. How to Install a Honeywell Ultraviolet Light Treatment System
    Prevent mold and algae with a disinfectant UV germicidal light.
  7. How to Install a Honeywell Ultraviolet Light Treatment System – Part 2
  8. How to Clean and Straighten AC Condenser Coils
    Outdoor compressor unit maintenance.

Evaporator Coil Cleaning Methods

I’ve written several tutorials about cleaning AC evaporator coils:

  • How to Clean AC Evaporator Coils with an aerosol spray foaming cleaner and overview of the various parts of the air handler.
  • Heavy Duty AC Evaporator Coil Cleaning using a professional coil cleaning solution and pump sprayer. It also shows how to inspect the interior side of the coils with a high intensity flashlight check to know if they are blocked with dirt or mold.

The above methods do work well to clean and disinfect the coils if the AC system is well maintained with regular air filter changes using quality filters. Remember – anything that makes it past the air filter may get caught on the coils. However air conditioners are often neglected and homeowners don’t realized there’s problem until the system stops cooling, usually because the coils are frozen over with ice due to insufficient airflow through the coils. Dirt and dust accumulation on the coils also promotes mold growth by providing a food source and moist media to grow on that can cause a “gym sock” odor.

When the evaporator coil case front panel is removed the outside (or downwind) of the coils may look shiny and clean but the interior (upwind) side can be dirty. If your evaporator coils are very dirty you’ll need to clean both the outside and inside faces of the coils. Your cleaning options are:

  • Depending on the construction of your coils, it may be possible to remove the front cover plate as explained in this tutorial. This is the easiest and lowest cost solution.
  • If the front cover plate cannot be removed due to refrigerant line obstructions, it may be possible to carefully slide the evaporator coil and condensate drain pan forward enough to access the coils through the bottom of the drain pan.
    This can be done only if the copper refrigerant lines to the air handler are long enough to be flexed without kinking or stressing the coil connections. It’s a two person job because the front of the coils and pan must be supported and you risk damaging the refrigerant lines. The condensate drain line and possibly the furnace vent pipe must also be disconnected. I don not recommend the homeowner attempting this cleaning method due to the level of difficulty and cost of hiring a professional to fix an error. However it is less expensive compared to cutting the refrigerant lines and removing the coils for cleaning if performed by a HVAC technician (next bullet).
  • The most expensive option is to hire an HVAC service and repair company to remove and clean the coils.
    The refrigerant must be drained and captured, the copper lines cut and the coils taken out of the system for cleaning. After cleaning and re-installation, the refrigerant lines are reconnected, evacuate the air and recharge the system. This is a major repair and I’d prefer to have a new evaporator coil installed rather than mess with the old coils.

How to Clean Inside of AC Evaporator Coils

My home has two identical Heil central AC systems – one in the attic for the 2nd floor and this unit in the basement for the main floor. It’s now July and hot in the attic so I’ll be working on my basement air handler.

The manufacturer label on the coil case panel states:

International Comfort Products Corp.
Lewisburg, TN USA 37091
Cased Evaporator Coil
Model No. EED36B15B1
Mfg. No. NEED36B15B1
Design Pressure 300 PSIG
Refrigerant 22

Remove the Evaporator Coil Front Cover Plate

I began by turning off the thermostat (my Honeywell touchscreen thermostat has Heat/Cool/Off modes) and shutoff the electricity to the air handler to prevent the blower fan from accidentally turning on.

I next removed the coil case panel to expose the evaporator coils. The front cover plate on my coils is fastened with 5 hex head 1/4 inch screws (red arrows); two screws are obscured by the suction manifold in this photo:

AC Evaporator Coils Front Cover Plate

AC Evaporator Coils Front Cover Plate

Notice the rust on the metal frame along the front of the condensate drain pan in the above photo. The rust is caused by condensation on the bottom of the plastic pan from the small amount of chilled water standing in the pan. Because there isn’t a gasket between the plastic pan and metal frame, air blows through the crack pushing the condensation to the front. The coils and drain pan simply sit inside the coil case. I lifted the drain pan up about 1/2 inch to check the plastic pan for cracks. This system is nearing the end of it’s useful life at 12+ years old. I’m getting quotes to replace the gas furnace and AC in the Fall because if something fails I’m not going to spend money for a major repair on such an old and less efficient system.

The two other 1/4 inch sheet metal screws are behind the suction manifold in the follow photo.

Referring to the following photo: High pressure / high temperature liquid refrigerant from the outdoor compressor/condenser unit flows into the coils through the liquid line where it’s flashed to a low pressure / cold gas by the restriction in the capillary tubes. The gas leaves the evaporator coils through the suction manifold and flows back to the compressor/condenser unit.

AC Evaporator Coils Front Cover Plate Screws

AC Evaporator Coils Front Cover Plate Screws

The coil baffle plate screw attaches to the coil cover plate. The screw is somewhat tedious to remove because of the narrow gap between it and the coil case frame. I used a 1/4 inch combination wrench to (slowly) remove the screw:

AC Evaporator Coils Baffle Plate and Screw

AC Evaporator Coils Baffle Plate and Screw

I could only turn the wrench a little at a time but was able to remove the baffle plate screw. Take care not to drop the screw. I found that my screw remained captive in the baffle plate which flexed upward as the screw is loosened:

AC Evaporator Coils Remove Baffle Plate Hex Screw

AC Evaporator Coils Remove Baffle Plate Hex Screw

The two screws behind the suction manifold are removed with the small wrench where my socket wrench and nut driver couldn’t reach:

AC Evaporator Coil Front Plate Removal: Screws behind the Suction Manifold

AC Evaporator Coil Front Plate Removal: Screws behind the Suction Manifold

I used a 1/4 inch socket on my nut driver to quickly remove the bottom three cover plate screws. Note the size and type of each screw because the screw for the plastic drain pan was different than the others:

AC Evaporator Coils - Front Plate Removal with Nut Driver

AC Evaporator Coils – Front Plate Removal with Nut Driver

The evaporator coil front cover plate dropped free after removing the 5 screws:

AC Evaporator Coils Front Cover Plate Removal

AC Evaporator Coils Front Cover Plate Removal

The cover plate was tricky to wiggle (“maneuver” is probably a better word) out from behind the suction manifold and capillary tubes. Work slowly and carefully to prevent damage to the refrigerant lines. Do not force the plate. I got it out by trial and error, moving it a little at a time. Basically I tilted the plate to the right and up, then slipped it out to the left as shown:

AC Evaporator Coils: Wiggle out the Cover Plate

AC Evaporator Coils: Wiggle out the Cover Plate

The coil cover plate is removed:

AC Evaporator Coils - Front Cover Plate Removed for Cleaning

AC Evaporator Coils – Front Cover Plate Removed for Cleaning

Good lighting is a tremendous help and I’m using a 1000 Watt twin halogen work light. The downside is the lights get extremely hot, but I can see in every nook and cranny.

1000 Watt Twin Halogen Work Lights

1000 Watt Twin Halogen Work Lights

Here’s the evaporator coil front cover plate on my workbench with the socket wrench, extension bar, 1/4 inch socket, nut driver and 1/4 inch combination wrench I used to remove the coil case panel and cover plate. Notice two oval holes and longer drain pan screw. When reinstalling the cover plate, install the two upper screws in the oval holes last.

A-Frame Evaporator Coil Front Cover Plate

A-Frame Evaporator Coil Front Cover Plate

This project is continued in AC Evaporator Coil Cleaning with Pump Sprayer and Brush.

All the Best,

Bob Jackson

Copyright © 2018   Reproduction strictly prohibited.


  1. george October 15, 2014 at 12:12 pm - Reply

    Mr Jackson –
    I am out of words and the only onesI can say are: Splendid, splendid, splendid!
    I have read 3 of your projects (one being “Chimney Leak”) and have learned so much that I became comfortable to do the work myself. Your thought process, procedures, pictures and demonstration are priceless! You are truly amazing…
    Keep up the good work!
    (Dallas, TX)

  2. Chef Bill September 17, 2015 at 9:45 am - Reply

    Your descriptions, pictures,how to guides….so helpful, I ‘ve been a home owner for 3 going on four years. Learning is exciting to me and your how to guide on fortunately my exact AC system has me excited for my day off!!! Ready to get to work on it and learn yet another task of home ownership!! Thank you!!!

  3. James November 16, 2015 at 7:21 pm - Reply

    Great descriptions, and pictures. I was able to clean my systems and was able to remove the stale air smell that emanated from the unit even time it cycled.


  4. wnm June 9, 2016 at 12:19 am - Reply

    Thanks for the info. I dug into my Coil which likely hasn’t seen the light of day for twenty years.

    What a bear.

    First, the people who put it in didn’t leave any way to access the coil chamber. 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.

    When I finally got to the underside of the coil, I found that it was blanketed with dirt and hair? I pump sprayed it out with a 40% mixture of Simple Green, the shop brush and a soft toothbrush (the only way to reach the top of A frame layered in hair). The hair came out in sheets and big clumps.

    After cleaning and rinsing it this way at least 6 times, I followed up with a foam cleaner then rinsed it all down again with water. I went a little overboard but I don’t plan on doing this again soon. The whole procedure took 3 days on and off. And, I still have to replace the snipped pieces for reassembly.

    Thanks again for the info.

    • Bob Jackson June 9, 2016 at 7:33 pm - Reply

      That cleaning job required a lot of determination and skill! Have you noticed a major improvement in your AC system’s performance?

      > 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 still have to replace the snipped pieces for reassembly.
      Buy some galvanized sheet metal and cut a mending plate that spans the two pieces of the cover plate. Lay the parts on the workbench and mark positions for hex-washer-head sheet metal screws where they won’t be obstructed by the refrigerant lines nor impact the coils, then drill pilot holes. Slip the cover plate back onto the evaporator coil then fasten the mending plate with screws.

  5. wnm June 9, 2016 at 11:36 pm - Reply

    So far, I haven’t turned it back on yet. I still need to replace the furnace filter/check the fit of the new filter from inside the fan compartment. The filter that was in there was bowing slightly. Not enough to cause a lot of dirt leakage but it’s something I would prefer to eliminate completely after doing this job.

    The coil cover pieces only ended up having about a half an inch gap horizontally after I straightened the cut/burrs up outside the unit. After cleaning, I replaced the bottom piece placing foil tape on the rear spanning the gap. I then replaced the top piece which mounted onto this rear tape and then also foil taped the front. The two sides of the tape gap are also joined together obviously.

    I’ll definitely need some mender plate on the sheet metal panel. I’ll have to recut the piece to square it out. Some more foil tape to follow reinstallation.

    Thankfully, I also have a bedroom window unit which takes on the blunt of the cooling load!

  6. Irene M Sylvester August 3, 2016 at 12:32 pm - Reply

    I was very happy to find this article. I have an ac man coming tomorrow and now I know what he should do to clean my system.

  7. Roni June 1, 2017 at 1:00 am - Reply

    I live in an apartment where the evaporating coils (fins) have never been clean. The whole apartment smells like something crawled inside the ac/heater unit and died. I changed the air filter and decided to try cleaning it by spraying Clorox clean-up spray directly on the coils. I let it air dry for a few hours before putting the cover back. I have never done this so I didn’t do a good job at cleaning it. I was afraid to end up with a puddle of water and damaging the unit. My question to you Bob is will spraying the coils with the undiluted Clorox spray damage or cause a fire when the unit is turned back on? I would really appreciate the information and advice.

    • Bob Jackson June 1, 2017 at 8:39 am - Reply

      HVAC maintenance is the responsibility of the landlord. You should contact the apartment management for service issues because you may be liable for unauthorized work or damage.

      Evaporator coil fins are aluminum. Household bleach is a diluted sodium hypochlorite solution that will corrode aluminum. A less than < 20% concentrate effect on aluminum is rated as having a "D-Severe Effect” in the Aluminum Chemical Compatibility chart.

  8. Ryan June 13, 2017 at 5:35 pm - Reply

    Thank you so much for this information! I am going to attempt cleaning mine tonight, It’s hot in Chicago, but I don’t see and end in sight and my AC is struggling!
    The situation I have is that I also have my drain and copper lines going straight through an access panel and it’s sealed so no easy way to remove it. I was able to get a corner bent back a bit to look at it and I can verify it’s filthy. I also have about a 1 foot section above the furnace but below the coil that this panel opens up into. Can I clean it well enough from below or would you recommend I cut the panel higher so that I can see above the coils too. (I have an upflow furnace).
    Alternatively I can cut a new panel on the other side. I purchased a 2′ x 3′ sheet of steel, foil tape, indoor coil cleaner, and sheet metal screws for the job.
    Thank you in advance for any tips!

    • Bob Jackson June 13, 2017 at 6:31 pm - Reply

      If you’ve no other choice cut an access panel on the back side of the evaporator coil case. What’s the coil make and model #? Is it an A-coil or N-coil? You can e-mail pictures to bob[at], replace the [at] with the @ symbol.

  9. Ryan June 19, 2017 at 9:16 pm - Reply

    I’m curious about whether it is possible to clean the evaporator coils that are otherwise unable to be seen. It is a ceiling mounted ACNF Goodman air handler that has the blower mounted/bolted to it, giving no access to the coils. Is this something common? I am able to see the drainage pan and it is rather disgusting. Might there be an alternative way to see/clean the coils, or is dismantling it the only option?

    Thanks in advanced,

    • Bob Jackson June 20, 2017 at 12:50 pm - Reply

      The Goodman ACNF ceiling mount air handler is an integrated unit with a blower motor, electric heater and slab evaporator coil. Most of the dirt will be on the interior side of the coils facing the blower. Cleaning most likely requires disconnecting the air handler (electrical and refrigerant lines) then taking it apart. Contact an HVAC service company to decide if cleaning is feasible versus replacement.

  10. Ashley denton July 26, 2017 at 12:31 pm - Reply

    Is there any way to clean my evaporating coils without taking them out I’m afraid I will mess something up if I try to take it apart I don’t have the money for someone to do it for me or for them to fix it if I mess it up and what kind of cleaner can i use on it it is so dirty and caked up with stuff I got some off with my hand but it needs to be cleaned very good I don’t know much about my unit just that it’s very old and it has a furnace for the heat it has a box outside and all the stuff that needs to be cleaned inside of one of my walls in my mobile home I would really appreciate your advise

  11. Bill November 10, 2017 at 9:03 pm - Reply

    Is there a brush available to clean the inside of the evaporator coils long enough to insert from the top opening without harming the fins? If so, where can it be purchased?

    • Bob Jackson November 11, 2017 at 2:43 pm - Reply

      By “top opening” do you mean to reach in from the left & right outer sides of the A-frame coils to get to back of the cabinet? It was awkward to squeeze my forearm beyond the suction manifold but I made it. I realize that some coils are obstructed by lots of refrigerant tubing with no forethought about maintenance access.

      Try duct taping a 3/4 inch diameter wood dowel to the handle of the flocked brush to extend your reach. Lay the dowel along the brush handle and wrap duct tape at the end of dowel and by the base of the handle so there’s no wiggle. As always work carefully with a light touch. Wood dowels are available at the home improvement store. Saw the dowel shorter if needed for better maneuverability.

  12. JD May 4, 2018 at 9:58 pm - Reply

    The worst mistake I ever made was replacing my 18 year old HVAC system with a new, high-efficiency model. (I was trying to get the expense out of the way pre-retirement.) I can view a graph of my electrical usage and the spike on the date of changing the unit is dramatic.

    I am very concerned that the only thing high-efficiency about the newer HVAC equipment is the label and I can only imagine how sorry the next generation of equipment will be. My suspicion is that this was all hype to get rid of that “horrible” refrigerant gas that rarely leaked.

    Your cleaning tutorial is well done. Thank you.

    • Bob Jackson May 5, 2018 at 3:16 pm - Reply

      Have you called your HVAC dealer to determine why the new high efficiency system is using so much electricity? Was the installer factory authorized & licensed? I suspect the your new AC was installed correctly but you may have a problem in your ductwork:
      * Return air ducts are ducts too small starving the new unit for air.
      * Break or leak in your ducts wasting air.

      A problem like yours shouldn’t be hard to identify.

      My new Bryant Evolution units are wonderful! Ice cold and my electric bill dropped 20%. See Old Central Air Conditioning Replacement with New Bryant Evolution High Efficiency System for details.

  13. Karen May 21, 2018 at 4:01 am - Reply

    If the inside of the A coil is dirty, is it possible that some debris inside could be maneuvering the condensation run off someplace else other than the drip pan? I have a small leak somewhere but it’s not from a backed up drain pipe, It’s driving me insane but I’m worried to open that portion because of all the fancy tubing around it. I was watching your diagram to see if it’s possible for me to attempt this. I’m scared lol

    • Bob Jackson May 21, 2018 at 8:17 am - Reply

      Condensation normally wicks down the surface of the coils into the condensate drain pan. If the interior surface is dirty / fuzzy then the condensate will drip off the fuzz into the air handler instead of wicking to drain pan. You can check if the interior coils are dirty with a flashlight and hand mirror.

      The other possibility is a plastic drain pan could be cracked or a metal pan rusted through.

  14. Skt August 18, 2018 at 10:20 pm - Reply

    I uesd outdoor coil
    Cleaner inside evaporator coil and i did not dilute it. I sprayed water after 10 minues to rinse the faom. Now i am worried how much damage i did to the coils. My unit is 4 years old.

    • Bob Jackson August 19, 2018 at 6:46 pm - Reply

      What type of coil cleaner did you use? Nu-Calgon Evap Pow’r C coil cleaner as recommend here is only slightly alkaline so likely no harm was done.

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