How to Clean an Air Conditioner and Remove Mold | Allergy

How to Clean an Air Conditioner and Remove Mold

by Allergy Guy

Air conditioners can be excellent mold breading grounds. dust gets deposited on the cooling fins, then becomes damp because air conditioners condense water out of the air. Damp dust is a pretty good medium for growing mold. The mold may not grow all that well when the air conditioner is running and cold, but between cycles, and during longer periods when the air conditioner is not needed, the mold can have a real field day.

Cleaning your air conditioner regularly improves your health by removing moldy dust, and improves the efficiency of the air conditioner.

Donald Grummett has provided this article on how to clean an air conditioner.

Very little is required to clean a window air conditioner, except lots of patience. If patience is something you lack then it is a job you should turn over to the local appliance serviceman.


  • Tin can or container (old muffin tin works well also)
  • Vacuum cleaner
  • Long handled brush (an old toilet brush works well)
  • Oil can
  • Rags
  • De-greaser or spray detergent
  • Selection of screwdrivers (Philips, Flat bladed, 1/4″ socket head)
  • Fin tool (optional)
  • New filter (if disposable type)

Air Conditioner Cleaning Procedure

1. Start by removing the filter from the front grille. If it is a disposable type simply replace it with a new one. Other types are made in a plastic frame and can be cleaned and reused. To clean a reusable type lay it flat in the sink and sprinkle surface with laundry detergent. Then cover with about one inch of hot water. Just enough so the filter is submerged. Soak for 15 minutes. Remove from water and rinse with warm water. Hang up to dry while proceeding to next step.

2. Next, remove the front grille from the main body of the air conditioner. They usually pivot on 2 spring clips at the bottom. It is usually removed by pulling the grille gently forward while pushing it down at the same time. If there is resistance then look for hidden screws. Look near the top edge of the grille or behind the control knob door. Once removed place the grille aside until later.

3. Carefully remove metal cover of air conditioner to expose inner workings. Once all the screws are removed lift the cover straight up. Do not let it hit the other parts as it can have sharp edges.

This is where the old can comes in handy (ice cube container or muffin tin works well also). Use it to keep track of all the screws you will be removing. An air conditioner will often use a number of different types and sizes of screws. Segregate them from each other or confusion will result when we start reassembly.

4. Check the fan motor for any oil holes or oil plugs. If the motor has oil plugs they are usually rubber. Use caution when removing because the rubber may have become brittle. Often they will break off in the oil holes resulting in a blockage. If this occurs try to remove the broken plug by using a pin, or the tip of a small screwdriver.

Once the fan motor oil holes are exposed add a few drops of oil to each end of the motor body. Use a general purpose (3in1) oil or clean motor oil. A #30 oil is sufficient.

The natural tendency is to over-oil. Too much lubrication is as bad as not enough. Therefore only 3 or 4 drops on both ends of the motor body is sufficient. Add the oil slowly, pausing a few seconds between each drop. If you add it too quickly over-lubrication will result.

5. Use the brush to remove surface dust and dirt from the evaporator (front fins). Use an up and down motion. Do not go side to side or allow the fins to be bent over. The fins are very soft aluminum and can be easily damaged.

Once surface dirt is removed, spray with de-greaser or cleaner. There is a good product on the market called HVAC cleaner. As the name implies it is meant for Heating, Ventilation, and Air Conditioner coil cleaning. If this is not available Fantastic spray cleaner used in kitchens and bathrooms works quite well.

Let stand about 15 minutes or as per instructions on de-greaser can. This will allow cleaner to loosen any hidden dirt. Remove dirt and excess cleaner by slowly pouring warm water into fins. Do not allow the water to enter any electrical connections or components that may be near the coil. As an added precaution cover the motor with one of the cloth rags. to protect it from the water.

Do not use any form of high pressure air or water because this can drive dirt farther into fins. Also, use extreme caution as these coils are filled with high pressure refrigerant.

6. Straighten any bent fins. Use a fin comb if available. If no fin comb then use something soft such as a Popsicle stick. Straightening the fins will increase the efficiency of the air flow through the coils. This adds to the overall cooling effect produced by the air conditioner.

7. Repeat steps 5 and 6 for the condenser (rear fins) coil. A plastic cowling usually surrounds the condenser fins. If so, check the top edge to see if it will lift or open. If it opens this will allow easier access to the condenser fins. Again use caution because the condenser coil is also filled with high pressure refrigerant.

8. Wipe any dirt buildup from both fan blades using a soft rag. Do not bend blades. This would cause a vibration that would harm the motor.

9. Vacuum all surfaces including front and back of grille assembly. Do not forget to vacuum underside of metal air conditioner cover. If the cover contains air holes clean them thoroughly. If necessary use a damp rag. Also use an old rag to remove any debris build-up from the base.

10. Drain any water left in the base and allow it to dry for few hours.

When completely dry plug in air conditioner and test operation. If everything appears okay unplug and reassemble.

Once reassembly is complete, retest operation to ensure replacing the cover has not affected anything. Adding the cover will tend to twist the frame and can cause interior parts to move out of alignment. This can cause the fan to become noisy. To correct for this problem remove the cover and realign to the main body of the air conditioner. Reinstall the cover and test for noises every time 2 or 3 additional screws are added to the cover.

Finally, cover air conditioner with plastic wrap or an old blanket. Store in a warm dry area. Raise it from floor slightly by placing onto a couple of pieces of wood. This will protect the floor from the metal edges of the air conditioner, and also protect the air conditioner from moisture.

Repeat this simple procedure yearly. If you do, the machine will be ready for many more years of dependable service.

By Donald Grummett (of Ottawa-based MG Appliance Repair Services)

NOTE: to prevent or at least reduce this problem in the first place, see Prevent Mold Growth in Air Conditioners

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{ 44 comments… read them below or add one }

1 AussieCate45 July 17, 2012 at 11:32

Below is a link to an article with advice on preventing the growth of the mould in air conditioners – don’t be put off by the adverts, they are not trying to sell you anything in the article – it is simple straight forward advice and seems to me to make a lot of sense. Fortunately my air conditioner has a sleep setting I can use for the fan, that turns off automatically after 2 hours. If yours doesn’t, a timer between the a/c power plug and the outlet would be one simple work around.


2 abidemi June 6, 2012 at 06:18

I jst finish servicing a 2hp sharp split unit so I dismantle it by steam the fin so I dismantle it but after I couple it bck again it not workin at all so wat will I do thank.


3 Allergy Guy June 6, 2012 at 20:11

Sorry, I can’t help with troubleshooting equipment


4 Sandra May 26, 2012 at 15:48

Well, this clearly won’t work with our two Haier window units as they do NOT come apart. We looked everywhere for hidden screws, etc. We even called Haier and were told that no, the front does not come off. It’s just a one piece unit. So, how now, do we clean these mold repositories? *Piece of advice: DO NOT EVER BUY A HAIER A/C!


5 Shannon May 25, 2012 at 22:44

Recently installed my frigidaire low profile air conditioners. My father stored them during the winter in a bag and they have a horrible smell now! Are they ruined? They are around 300 each, should I just purchase new ones or would servicing them a possibility? I don’t even know who to call to have them professionally cleaned.


6 Allergy Guy May 26, 2012 at 00:43

If they run, they’re not ruined. See reply above for ideas on who to call re cleaning.


7 Katie May 24, 2012 at 16:29

who do you hire to clean and get mold off of window air conditioners?


8 Allergy Guy May 24, 2012 at 16:58

I would suggest an air conditioner company or maybe a small appliance company.


9 vicki November 27, 2011 at 02:43

I’ve used window units for years and never taken them apart to clean, except the recommended cleaning in the product booklet, but never had mold problems from them. The smaller ones don’t cost very much, so cleaning those front fins and replacing every couple of years is my solution without having to take the body off and deal with the styrofoam. Maybe pouring in some well diluted bleach or herbal water into the bottom and letting it drain and dry also would help?


10 Allergy Guy December 2, 2011 at 09:18

You’ll get mold in your air conditioner after a few months, maybe weeks of operation. Most of the problem is on the fins, the pan at the bottom may be less of a problem unless it gets dirt from outside.


11 Achoo September 30, 2011 at 22:00

People have been talking about bleach and water for years to handle mold, but when a company came here to clean some up from a faulty built back door leak, they failed to do the job with bleach..much to my big problem now…
When I was being tested for allergies I was told to use Grapefruit Seed Extract to obliterate mold….especially in the fridge, and I would rather have that smell in an AC unit as well….for people who see it, it must be cleaned up, after a while, your immune system will react badly from it, mine is, but I have found the problem and is getting cleaned up. Also there is a drain pipe that needs to be checked, it will cause a mildewy smell to come in the central AC vents, this can get clogged from what I understand, and this can be bleached out…


12 Stacy August 26, 2011 at 12:37

My AC window unit is a Frigidaire, just purchased this season. Recently I’ve noticed that moldy smell. I clean the inside filter pretty often, as it has a “clean filter” light that comes on after so many hours of use. I went outside to take a look, and down in the back of the unit where you can see the styrofoam, etc, there is pink mold all over the styrofoam and down in the bottom it appears to be muddy looking, rotting leaves. It looks gross. I dont understand why they would make this unit with such large slots on the top that allow leaves to make there way down into the unit. Is this unsafe, and what possible symptoms could this cause? We also have a problem with window condensation in the winter, and black stuff around the window caulking, but we have this every year when it gets cold outside. We have come down with cold like symptoms (runny nose, tiredness, itchy throat and watery eyes) that just dont seem to be going away. Does that sound like a mold reaction?


13 Allergy Guy September 2, 2011 at 20:19

The symptoms you describe could be mold-related.

One thing you may try with your air con is when you want to turn it off, leave the fan running without cooling for 10 minutes or so to dry it out. That should reduce mold problems. Maybe you can find a way to prevent leaves from getting into the unit while still allowing adequate air to pass through the unit.


14 Errol January 11, 2012 at 17:30

Hi I live in Texas near Houston close to the Gulf of Mexico. Last summer we had a the worst marsh mosqitios that I can ever remember. Well they lived in my ac unit on the outside. So when I got a chance I used my water hose to flush them out (never took the metal case off) when I was doing that there were leaves in there they also came out after some more water spraying. I went to The Home Depot and bought a roll of aluminum window screen as it is flexible, I put that around the sides of my AC and on the back…It keeps the bugs and leaves out so you might want to try that all together it cost me under 15 dollars you should tru that 🙂


15 Dave March 29, 2011 at 01:38

You can bleach the styrofoam as mentioned above. Just bleach it enough to get rid of the mold as the styrofoam will oxidize very slightly as well. I found that adding a portion of baking soda and calcium chloride (driveway deicer or salt) or sodium cloride resulted in a fast working solution that prevented further mold by leaving a bit of salt and carbonate behind. Keep the calcium chloride or sodium cloride off the aluminum fins as it will corrode them.


16 Allergy Guy March 29, 2011 at 12:57

Thanks for the salt/baking soda tip to reduce future mold build-up, that’s a great idea!


17 Silvia March 27, 2011 at 13:27

HI. Our A/C is one year old SHARP AF-S155NX and it’s about time to turn it on. I wanted to clean it before, since it has mold inside and around the fan. The problem is the inside is Styrofoam and it’s in one big piece. I can’t imagine how I could replace that. Can u order it from the company? Or I just have to try to take it out and clean it with bleach? Thank you.


18 Aklis Thheodore March 25, 2011 at 10:27

My A/C goes off after every 15 to 20 minutes, had to continuosly put the main switch off and on before it restarts work. Please i need help, my repairer is not available. Thanks!


19 Allergy Guy March 25, 2011 at 16:25

Sorry, can’t help. This website is about allergies, not conditioner repair.


20 Lou Minn October 2, 2010 at 13:53

I just uninstalled a window unit air conditioner (by myself…a bad idea) and got whatever water/moisture that was in the unit all on my living room rug. The unit is now on a plastic bag in the closet. Not a ton of water, but just wondering if that’s going to muck up the unit? Also, how dangerous is that AC water for breeding mold?


21 Allergy Guy October 4, 2010 at 11:59

Storing the AC unit in a plastic bag is a BAD IDEA! That will help the mold grow like crazy! You must let it dry out, then store it without the bag.

AC water is prime for mold breeding because not only is there moisture, there is dust collected from the air to feed the mold.


22 donald powell July 3, 2010 at 11:15

we have mold on our window air conditioner on the intake air vent. we can clean the vent and front cover but how can you get the mold from the inside where the air goes in. we are looking into getting a dehumidifer. hoping that will help out. thank you for your help.


23 Allergy Guy July 3, 2010 at 11:53

Hi Donald,

To get the mold from inside, you have to disassemble the air conditioner. If you’re not comfortable with that, hire someone to do it.

Air conditioners do remove moisture from the air, so I doubt you need a dehumidifier as well.


24 CjMohr May 19, 2010 at 13:47

I have just been told that my a/c centrail air unit has mold growing on the coils? Is this possibe? What can I do? I do not know where the coils are even located in a/c unit. Is this a fixable problem for one time or do you have to spray something every month? I have had a service agreement with a company for several years; this h
as just been bought to my attention. The tecks wanted to install a light i think, at $499 but is that right?
Pleae give me any information you can.
Thank You


25 Allergy Guy May 19, 2010 at 14:01

I’m not an expert on central air conditioners, so I can’t give you definitive instructions on how to fix it (besides, every model is different).

Yes, mold can grow on the coils. This is more likely when there is a problem with the air filter: if dust bypasses the filter, it will stick to the wet cooling coils, and provide a perfect environment to grow mold (dark, moist, lots of nutrients, and not too cold between cooling cycles).

I suggest you get a second technical opinion – have them look at the filter. It should be possible to clean the coils and fix things so this never happens again. At least in my opinion. To me, the %400 UV light is a lazy solution that doesn’t really fix the root problem, but does solve the company’s problem of how to sell more UV sterilization lights. It may well work. On the other hand, the back side of the coils will be in shadow, so I doubt it will 100% fix the problem.

Hope this helps.


26 Guest August 23, 2009 at 15:26

bleach styrofoam

Soaking the styrofoam in bleach. I did weigh it down and soak, but you need big bucket to fit. It worked a little, stunk like bleach after. Also may destroy the styrofoam a bit. In the end, I painted the remaining styrofoam pecies (to remove oder) with exterior latex house paint and put ac back together. Sold it for $20. This is after using it for 10 yrs never cleaning.


27 admin August 23, 2009 at 17:18

Bleach smell fades

The bleach smell should not last too long.

You have to be careful what paint you use as that can destroy styrofoam. Don’t know if exterior latex paint would be OK or not.

Another problem with painting is that as it ages, it will likely allow moisture in through small cracks, but to allow it to dry effectively. This could cause an even bigger mold problem.

Finally, selling someone else your problem is bad karma.


28 wow May 11, 2011 at 11:01

Wow… If the air conditioner wasn’t good enough for you, you certainly shouldn’t have SOLD it to someone else. I hope you at least told them that you’d never cleaned the thing, and then when you did you caused the styrofoam to be bleached, slightly deteriorated, and then painted. If you didn’t disclose that, then you’re not a nice person.


29 laura July 29, 2011 at 13:02

Just another reason I don’t like buying used items. Some sort of old saying like you are buying someones problems. How true! We have 2 small window units I haven’t tried opening them up to clean them yet. One is from last year the other was bought at the start of summer this year. I can see where they will need some deep cleaning perhaps before storage. I usually clean the inside grille thing, filter and outside fins.


30 admin March 24, 2009 at 13:33


I suggest you replace the styrofoam.

Unless it is expensive closed-cell foam (unlikely) the mold will probably be within the styrofoam as well as on top.

You could also try:
* Soak the blocks in bleach. You’ll have to put them in a bucket of water and about 1/4C bleach, weight them down, and let them sit.

* Leave them in the sun for a few hours (remember to turn them so the sun gets to all moldy surfaces). This may get most of the mold. Do this too often and for too long though, and the foam will deteriorate and crumble. I don’t know how much is too much.

Hope that helps!


31 Brenda Breuer June 23, 2011 at 14:52

Last year, after having my air conditioner for about 2 years, I noticed the moldy smell coming from it. This summer I had a professional clean the machine. He said there had been a tremendous amount of mold in it, and he was able to get most of it out, but not all. He said that the only way to get out all the mold would be to have the air conditioner brought to the shop for steaming and cleaning. This would cost over $200. He also said that although he has worked with air conditioners many years, he just started to hear about air conditioner molds last year–and indeed, it is only my most recently purchased air conditioner that has this mold. This makes me think that something might have recently changed in the way air conditioners are manufactured. I would think there should be a warranty against this. I’d appreciate your feedback.



32 Allergy Guy June 23, 2011 at 17:03

I think mold has always been a problem in removable air conditioners, because they get full of dust, which gets wet due to condensation generated in the process of any kind of air conditioning.

It could be that the problem is now worse due to inferior filters. The filters are there primarily to increase the efficiency of the air conditioner, but also help reduce mold problems.

It is also likely that people are more aware of mold problems and that there are therefore more service calls about mold in air conditioners. There may also be a change in some of the materials used in air conditioners that are more susceptible to mold.

It would be interesting to hear what the serviceman thinks of these various points.


33 Brenda Breuer June 24, 2011 at 12:57

So nice of you to respond so quickly!

Are you saying that the filters are inferior now, or were you implying that they might be, and that might be a reason for the recent increased reports of mold?

When I get a chance I will try to remember to mention your points to the serviceman.


34 Allergy Guy June 24, 2011 at 19:22

I was implying that they might be. I’m a generalist, not an air conditioning expert!

Most likely though, people are more aware of mold problems than they used to be.

35 Brenda Breuer June 26, 2011 at 09:20

I spoke to a friend of mine. He thinks that it could be that the air conditioner was installed at a slant that somehow captures the condensed water in a way that is conducive to creating molds.

36 Guest March 24, 2009 at 11:39

Mold inside the window AC unit on the styrofoam

How do we need to go about cleaning mold off the styrofoam that is inside the unit?


37 Guest February 14, 2009 at 08:27

getting rid of odor and mold

I think it’s assumed that the cleaning procedure outlined above be done after unplugging the unit and removing it from the window. Otherwise you would not be able to remove the metal cover.

I’m using my unit for the third year now, and last year I was fighting a sour, musty smell. I had been unable to remove the metal cover because a screw would not come out, so I cut the screw off with a hacksaw a few days ago. Now, after giving it a good cleaning, in the way described above, I am still having a bad odor. So I believe the instructions above are incomplete.

I believe it will be necessary to turn the unit over (after removing the cover, and also remove the bottom metal base to get access to the drip pan for a good cleaning. Not yet sure how difficult that will be, it probably varies from model to model. But I simply cannot go thru another year with that foul odor. If I cannot get the thing completely opened for a thorough cleaning then I’ll have to buy another unit.

I’ll be attempting another disassembly this weekend and will report back about the results. I live in East Texas, and with all the electronic equipment I have in my small bedroom it gets very warm very quickly even on nice days, so I have to use it even during February at times.


38 Guest February 12, 2009 at 18:02

you forgot an important thing

I would highly recommend to pull the disconnect or turn the switch off to the unit before you touch any fan for oiling.


39 admin February 12, 2009 at 22:56

You are right

I agree with you, thanks for the tip.

Actually, I recommend unplugging the unit – that way you know it is off for sure (you can see the cord dangling) and there is no chance of accidentally turning it on while you are working on it.


40 3D April 17, 2012 at 10:05

You forgot one key detail! Taking the air conditioner out of the window for cleaning. Unless we are assuming it is already not in the window because its been sitting in the attic for months. You should let people know its imperative that you take the AC out of the window if necessary to avoid losing any parts or the whole unit.


41 Allergy Guy April 17, 2012 at 22:23

Good point!


42 Anonymous June 8, 2008 at 13:18

Diagrams or photos

I’ve clean my a/c units repeatedly, and they still smell terrible. I am clearly missing something. Some diagrams, photos or video would be extremely helpful here.

Thank you.


43 admin June 8, 2008 at 18:38

Good point, but …

You are right that extra visual info would be helpful.

The main point of the article is that you can and should clean your air conditioner if you have $allergy$ problems.

This website isn’t about air conditioners, so I’m afraid we won’t be supplying videos.

Your best bet might be to take it in to a repair shop for cleaning.

I know that isn’t the most helpful of advice, but given the focus of this website, that’s the best I can do!


44 Allergy Guy June 27, 2011 at 08:38

Good point, Brenda.

The air conditioner should be sloped towards the outside so that condensation drains properly from the unit.


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