My Haier HPN12XCM Portable Air Conditioner, 12000-BTU air conditioner produces a horrible smell whenever it is in fan mode after I run it in AC mode.

To reproduce the problem, I do the following:

  1. Run the AC unit in AC mode for 20 minutes. No smell.
  2. Turn off AC mode and turn on fan mode. Smell slowly fades in over about 2 minutes.
  3. A horrible smell will occur for approximately 20 minutes and then go away. It appears for longer if the AC unit has been running for longer.

Interestingly, if I turn AC mode back on, the smell disappears within 1 minute.

I've attempted to disassemble the unit to find the problem. Some very minor damage was present to the coils on the lower half and those coils, when rubbed with a paper towel, produced the smell of rotten eggs on the paper towel.

The smell is not easily identifiable when it's in the air, but if anything, I would guess that it smells like a mixture of butt and that awful oil smell you sometimes find on railings outside.

What I've tried to fix the problem:

I've attempted to run the unit for 7 straight days in fan mode to no avail. When I ran the AC unit for 20 minutes after that, the problem reappeared.

Unfortunately, this makes my portable AC unit inoperable, since it needs to be in fan mode for 2-3 minutes before AC mode kicks in and the smell does not go away when the unit has been off for a while. The smell is so awful that it sticks in the room for hours afterwards even if it only runs for 2-3 minutes.

I've also tried unplugging both of the rubber plugs on the back. On a humid day, one produced a small amount of liquid. Today, despite the smell, no liquid. Also the lint filter on the outside of the unit has no lint on it.

This unit is a rental from my apartment complex. I've tried switching out the unit but they both had the exact same problem.

What could be causing this smell? Is there a way to fix it?

  • Since your "butt and oil" smell sounds like burnt motor windings I would have an electrician check it out this smell could be the start of a motor meltdown. Some really bad advice below. AC techs don't use bleach or acid based cleaners on the fins unless trying to wipe them out. Possibly a good answer If the moisture from the coils is dripping on to the pump and evaporating like @Zach answered they do make non chlorine tablets to kill the smell as the water drips into the "hot tray" on the compressor. This model said it worked as a dehumidifier to do that the water needs to be drained.
    – Ed Beal
    Commented Jun 8, 2018 at 10:12

3 Answers 3


I'd be careful with cleaners, the manual online specifically says not to use any harsh cleaners. Personally, I'd use my judgment on this though. I'm not sure how much you can get at the insides, but I'd try and brush the coils with an old toothbrush and warm water with a drop of dish soap.

I'd also see if I could clean the evaporation tank. Water condenses on the coils and drips down into the tank. Heat from running the unit should evaporate the water (just like your fridge) so it's normal not get much out of the drain hole. You should be able to take the lower drain out, spray warm water on the coils and see it drain out.

You should also wash the air filter weekly, it's collects dust and not just lint, so visual lint isn't a useful indicator of anything.

Personally, I'd never use the AC just in fan mode. If you want to just move air around, an actual fan is going to be more efficient.

If these are the only two rental units left from your apt complex, you might see if they'd buy a new one, or consider buying a new one yourself. It looks like a model similar to this is around $400, so depending on what you pay to rent it, it might be easy to recoup that cost in a short amount of time.

  • I would agree with the system running like a fridge but as a dehumidifier the water would need to be drained when I looked up Haier HPN12XCM it said it also worked as a dehumidifier.
    – Ed Beal
    Commented Jun 8, 2018 at 9:58
  • The manual mentions you only need to empty it if its extra humid or if it shuts off because it's full. I think in general it uses the heat from the motor to evaporate the water (most fridges do this) and then blows it out the window with the extra heat.
    – Zach
    Commented Jun 8, 2018 at 15:48

Unfortunately there are some kind of spores or bacteria growing inside the evap coils. When a portable window unit is installed it should be slightly tilted to the outside. This is to drain off some condensate. If it's not titled the condensate will foster nasty things to grow and they embed into the intricate fins of the evap coil. So if you can get it apart you can clean the coil with a special coil cleaner made for that. But after you clean it, I would disinfect it with alcohol. Or hydrogen peroxide, you have to kill that stink off because it can protect itself in a protein sheath. Kinda like bad breath is caused by bacteria, same kinda thing for your AC unit. When you say the lower part of the evap coil smells bad that is why I am thinking some condensate has sat there creating a perfect environment for the undesirables. So clean, disinfect, repeat if necessary because they have set up camp for the long term.

  • Two questions: 1. Could I potentially get rid of the smell by turning on the AC for an hour, draining it, running the fan for an hour and repeating a dozen times? Or would that make it worse? 2. Do I need specialized coil cleaner or can I use hydrogen peroxide spray cleaner? Commented Jun 7, 2018 at 7:05
  • You can try maybe an 10:1 mixture of bleach and follow it up with H Peroxide. Main idea is that whatever is in that coil protects itself so you have to break down the protection barrier (proteins) then kill it. Think of athletes foot. Once you get, you can hardly get rid of it. But it can be done.
    – vin944
    Commented Jun 7, 2018 at 17:06
  • Wear gloves and face. mask when mucking around with muck.
    – Yehuda_NYC
    Commented Jun 7, 2018 at 17:57
  • I don't think the smell would ever go away if a coil issue , mixing bleach and acid ( hydrogen peroxide) are you crazy @vin944 ? Both are A big no no on that aluminum fins in an AC unit and unless flushed there will be residue that can create a caustic cocktail (lethal gas). A simple non acidic coil cleaner is what we pros use. the description of the smell sounds more like over heated motor windings to me. But could be bacteria if the unit is not being drained since it is indoors. They do make tablets that won't damage the metal and kills gunkies.
    – Ed Beal
    Commented Jun 8, 2018 at 10:02
  • Easy with the trolling name calling Mr Narcissist Ed.
    – vin944
    Commented Jun 8, 2018 at 17:02

If it's not a dead mouse, your drain pan needs cleaning. Sometimes they are Styrofoam and plastic so no harsh chemicals. I'd take the cover off and use a hose and carefully rinse it without getting electrical components wet. You could add a few drops of bleach to the water (after the pan fills from use). Always unplug it to clean it!

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