Please save me from A/C Hell

July 12, 2018 12:11 PM

Why does my air-conditioner smell bad and how can I fix it?

My air conditioner (a Mitsubishi Mr. Slim mounted on the wall), has a horrible smell coming out of it that nobody can fix. It has been taken apart and deep cleaned many times but it always comes back. It's gotten to the point where I can't use it because it's so nauseating, which is not tenable in July. Sometimes the smell gets on the sheets and mattress, and as I sleep directly underneath it, this is bad.

Things we've tried:
- aforementioned take apart and professionally deep clean (all the coils), basically everything you can do for Wet Sock Syndrome
- trying running it for a long time on different temperature settings (fan, automatic, etc) for varying periods of time
- not running it at all for long periods of time
- Simply Green and soap and water
- cleaning specific parts and not the whole thing
- blasting the heat to dry it out
- cleaning the gutter outside the window behind it
- various odor absorbers
- having a bunch of dust/dirt removed
- hosing it down in the backyard (also done professionally)
- deep cleaning the rug on the floor underneath it (the rug smells good now at least)
- probably some other stuff I can't remember

Please help! The HVAC company no longer knows what to do and I can't call them again. They suggested using something called Odo-Ban but I have no idea if that will work given everything else they've done. Whoever solves this will be my hero.

posted by colorblock sock to Home & Garden (7 answers total)

OdoBan is amazing and available at Home Depot. It was the only thing that fully removed the mildew smell from the carpet in my car, so it may be worth a chance. I hope someone else has a better solution, but OdoBan is pretty amazing.
posted by needlegrrl at 12:21 PM on July 12, 2018

Idea: Chlorine tablets for drain pan/coil.

Is it very humid where you are? How does the unit drain? I'm wondering if that's what needs to be thoroughly cleaned out, or replaced. That smell could rising up via the drain line and backing into the unit.
posted by Iris Gambol at 12:30 PM on July 12, 2018

Am I correct in assuming the "Mitsubishi Mr. Slim" is a mini-split style AC, i.e. it has both an indoor unit (evaporator) and an outdoor unit (compressor) connected by refrigerant lines that run through your wall? You've gone to a lot of work to clean the evaporator, so I assume there were no obvious smells originating from evaporator after it was disconnected and cleaned. I might explore the possibility that the smell is originating from the opening cut for the conduit that runs inside the wall, not the wall unit itself. If the the refrigerant lines are not well insulated, it is possible that water has been condensing on the cold refrigerant lines and dripping down inside your wall, leading to mold or mildew growth inside your wall. Similarly, the condenser probably has a drain line, so I might check to see if there is any indication that the drain line has been leaking somewhere.
posted by RichardP at 12:34 PM on July 12, 2018 [1 favorite]

Response by poster: Don't wanna threadsit but yes RichardP it is a mini-split style. They shortened the drain line, took the unit off the wall, fixed an unrelated leak, and checked for any other leaks. We checked the drain line.
posted by colorblock sock at 12:39 PM on July 12, 2018

I called a plumber for a mystery mildewy smell that I thought was coming from beneath the kitchen sink. It turned out that my AC (on the other side of the wall) had a - I want to say u-bend? drain trap? - that is supposed to have standing water in it, but this had all dried out.
posted by Naanwhal at 1:06 PM on July 12, 2018

...fixed an unrelated leak

Can you elaborate? Perhaps there is mold/mildew or other damage inside the wall and while the A/C unit is not the primary culprit, it could be pulling air from inside the wall and blowing it out into the room.

I'm not advocating for cutting a hole in your wall, but sooner or later it may be useful to see what exactly is going on if all the other ideas above are not working.
posted by JoeZydeco at 1:25 PM on July 12, 2018 [1 favorite]

I'm not advocating for cutting a hole in your wall, but sooner or later it may be useful to see what exactly is going on if all the other ideas above are not working.

How about drilling a hole (behind the floor molding?) and using a cheap endoscope to peek inside the wall? I just got one (with lights on the end!) off of aliexpress.com for like eight dollars.
posted by wenestvedt at 7:01 PM on July 12, 2018 [1 favorite]