Even when the compressor is not running in cooling mode and just the fan is spinning it is producing a musty smell. Where could the smell be coming from and how can I clean it? This unit does not have a tank, it re-distributes the water in cooling mode.

  • I need a quick bit of advice. I cleaned the coils of my air con today with part bleach/water by spraying it through the coils. It appears the bleach mix was too strong though and the unit smells heavily of bleach. How can I neutralize the bleach smell? – Kol12 Dec 6 '18 at 10:49

What I have found is the drain has gotten plugged in tha back outside section, dust builds up and plugs the hole , the other thing I have found that causes portables to smell musty is when they are installed level. There is supposed to be a tilt to the back so the condensate will run to the back and drain outside. There are special cleaners for AC systems make sure to use non acid based cleaners and flush with clear water. Acid based cleaners are very hard on the cooling fins and can start corrosion that will shorten the units life. I would want to flush my unit if musty and make sure it is draining completely or the smell will come back after cleaning .

  • I only use the drain in heating mode, in cooling mode this unit re-uses the condensate by spraying it around. I don't think the drain is the issue in my case... – Kol12 Dec 1 '18 at 8:48
  • Recycling dirty water is a good way to create the smell you are talking about. In large commercial systems this has been the breading grounds for leigonairs disease. – Ed Beal Dec 1 '18 at 16:43
  • I don't think they would have designed a system to reuse the condensate if they weren't confident it was safe, but I suppose the reused water could lead to the smell in the coils. How are you meant to flush the coils on a portable with all of the electrics nearby? – Kol12 Dec 3 '18 at 7:37

Mold can grow on the components which are persistently wet from condensed water vapor. Google your specific model and see if you can get a procedure or even a Youtube video showing cleaning.

I would not use vinegar because it would corrode metal and the odor might persist. The usual active ingredient in most mold cleaner is some form of chlorine bleach.

For cleaning a/c refrigerator coils, I have always wanted to try hydrogen peroxide 3%, or even 4% or 7.5%. I would never use any higher concentration than 7.5%. Hydrogen peroxide is odorless and doesn't leave a residue. Fact sheet on hydrogen peroxide.

TX678G 7.5% Hydrogen Peroxide There may be regulatory restrictions on the purchase of hydrogen peroxide in larger quantities and higher concentrations due to its recent history of very, very serious misuse (production of improvised explosive devices using acetone peroxide).

Hydrogen peroxide is commercially available in 37% but the oxidizing effect of higher concentrations is much, much higher, and 37% hydrogen peroxide is a very dangerous substance. Even 3% should not be gotten in or around the eyes. Use eye protection even with 3% when it is being used for cleaning and could be splashed.


I would have thought that the portable a/c units that do not collect condensate in a reservoir or drain it by a hose to the outside would spray the condensate onto the condenser coils so that it would help cool the condenser and then would get incorporated into the hot exhaust air stream where it would be expelled to the outside. So you might have to clean both coils--evaporator and condenser.

  • Thank you for your reply. If I made a spray solution of 50/50 bleach/water is it safe to spray the coils? Would I just spray it all over the coils and wait for it to dry? Obviously the coils in a portable cannot be hosed down afterwards due to the electrics. – Kol12 Dec 1 '18 at 8:45
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    50/50 bleach/water might be too strong. Investigate this further. – Jim Stewart Dec 1 '18 at 9:57
  • Whatever I spray over the coils do I need to rinse it afterwards or just let it dry off? – Kol12 Dec 1 '18 at 11:49
  • Yes that is how they work, by spraying the condensate onto the condenser coils to help with cooling. Of course in heating mode it needs a drain line as usual. – Kol12 Dec 3 '18 at 7:33
  • I didn't know that these portable inside a/c units had a heating mode. I thought they were all just a/c to lower the indoor temperature. Does this model have two hose ducts--one to draw in outside air and the other to exhaust – Jim Stewart Dec 3 '18 at 18:54

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