MW4matic

It happened to me when I bought my 2010 luxury model. I thought it was molding in the a/c too but, I believed the cabin air filter (under the passenger footrest) needed to be changed. Give that a try.

fosterelli

From what I can tell, the blower is blowing air through the cabin filter, which then travels across the evaporator and into the ducting for a/c vents. At least that's what appears to be happening on my 2014 from having it apart. This would mean changing the filter won't help if you have the mold/mildew/fungus/bacteria issue, because (1) you're not removing the growth (2) the filtered air is immediately contaminated before it comes out the vents...so regardless of age of filter, you're still breathing (and smelling) nasty air.

CopterDude

I've had this issue with a couple MBZ. Found best way for me is take old cabin filter, cut filter off and keep just cover, spray a decent foaming AC disinfectant (I use Interdynamics Quest Oder Eliminator - Autozone 10.99 5/18), apply to inside duct area in front of evaporator, immediately put filter cover I cut away on, and wait 15 minutes to let foam do its job. Then start the car and run ac on low for 10 minutes. I'll also take the air inlet off under the hood on my E400 and give a couple extra shots of Lysol (pick a flavor) while cycling the vents through different positions (about a 10-second spray for each position). Turn off the car, install new cabin filter, and leave windows, sunroof, and doors open for about an hour to air out. This has always worked best for me. Don't really have the issue now that I live in Vegas, but I did have my E400 parked for an extended period after being in TX recently and it really stunk like a dirty gym bag dipped in vinegar and cat pee (you're welcome for the mental flavoring). Gave it the above procedure and smells brand new. Hope this helps you out.

Sumit Bhasin

Hi,
What kind of chemical did you use to get that smell out? Where can I get it? I'm in Houston as well. Kids won't get in the car cause it smells of stinky feet! Please help!

Sumit Bhasin

This product is listed for general AC cleaning. Would it work for auto ACs?

https://www.walmart.com/ip/Frost-King-Air-Conditioner-Foaming-Cleaner-19-oz/20703057?wmlspartner=wlpa&adid=2222222222802538827 3&wl0=&wl1=g&wl2=m&wl3=56163339369&wl4=pla-88828785369&wl5=9027720&wl6=&wl7=&wl8=&wl9=pla&wl1 0=8175035&wl11=online&wl12=20703057&wl13=&veh=sem

mleskovar

Perfect! Don't look a gift horse in the mouth

belarus27

There is only one way to get rid of the smell
and it is to replace the filter.
period.

mleskovar

You also need to spray a disinfectant into the system to get rid of any mold that may have collected in the airways. Do it without the filter media in place.

Oda112

I'm curious as to why you guys have issues with AC odor since our W212s vent the AC duct circuit entirely after the car has been sitting for 1h. The first time mine did that I was intrigued and thought there was something wrong with the AC control unit but posts here helped me get acquainted with the cleaning feature. I haven't had any smells in 1,5 years of ownership. The only issue with AC smell I've had was on my E46 coupe and after spraying some bacteria and fungus killing solution on the evaporator and running it through the system for 15 minutes the stink was gone. It's been 4 years since that treatment and I haven't any complaints from the current owner.
For those who already have the smell the drying cycle won't help. Fungus and bacteria treatment might help (maybe repeat after a few days if smell is still persisting) and definitely check if the drying cycle is actually running (liveoak described it very well in post 10).
I don't think this cycle can be defeated by anything, not even FL humidity , if it's running properly and the drain holes aren't clogged.

thefisch

My car does not vent the AC duct after it's turned off. I keep my car garaged and in 4 years I have never heard it run an hour or anytime after turning off. I believe the previous owner had a battery issue and that vent feature was turned off by dealer to avoid battery drain (as others have reported here). My drain tubes seem to work fine based on what I see coming out of them.

I have done a few rounds with Lysol before - spraying into the ducts, into the cabin filter housing towards the evaporator, into the air intake while running, etc. Also, taking out and spraying the filter itself and allowing it to dry. The smell returns once the Lysol smell wears off. Perhaps the smell with the spray foam lasts longer.

The only thing that makes a long term difference for me is to change the cabin filter - then the smell is gone. On two previous occasions of having the smell, I have taken video of my evaporator from inside the filter housing and it appeared completely clean - no signs of growth. If the source of the smell was in the ducts or the evaporator then changing the filter would not make a difference. While the cabin filter change interval is 2/20k, I find that the smell starts to return after about 18 months. It's starting to smell again in my case - filter was changed in January 2017.

I think the solution will differ for each of us. I still think trying Lysol or some equivalent is the cheapest and easiest first step. If that doesn't work long term, then next step would be a cabin filter change (good idea to keep old once in case that wasn't issue or for experimenting with). If those two steps fail to address smell, then the spray foam would be my last resort.

belarus27

There is an option to turn off that cycle ?? I would like to know what its called..as i also do have battery drain issues , that i believe might be caused by it

thefisch

There are posts from a few years ago about service tech turning that feature off to address battery drain. There was no TSB mentioned, but it seems like you need access to DAS to modify that setting.

Oda112

I'll take a look and see if I can find anything about this option. Personally I don't think it's very taxing on battery life unless the battery is already dying. The blower motor is a 12V with a max output of around 200W, but it doesn't sound like it's being spun at max speed during that cycle, my guess would be that it's drawing between 5 and 10 A during the drying operation, that's 6 to 13% percent battery usage depending on individual Ah ratings. Also there has to be a fail safe that prevents the drying cycle from starting if the battery charge is under a certain voltage. Unless there's something wrong with the ON duration of the drying cycle (like a sticking relay maybe) I just don't see how this could represent a battery drain issue and necessitate deactivation. Especially for people living in humid areas.

thefisch

Maybe turning mine back on would help my situation. But I don't have access to DAS and I'm not going to pay the dealer for that. Cheaper to replace the filter 6 months early.

mercerized

Hi,
I just recently purchased the MB HVAC System Cleaner; 8 oz Aerosol Can (P/N: MB-AQ1830002). AZparts and my dealership sells it. $23
I have a of smell coming out of the vents. Plan to soak my evaporator this weekend.

fosterelli

I'm happy to help people in the greater Houston area, just send me a PM and we can work out a time. I use Liqui Moly Active-2P A/C System Cleaner w/ gun (don't purchase, I have it all...or if you're not local, PM me and I'll get you hooked up). Basic steps are to remove cabin filter under glove box, use gun and spray tube & multi-jet wand, feed through filter inlet over to evaporator, spray evaporator surfaces. Run HVAC per instructions before/during/after service. Replace cabin filter with a new one. No drilling. No hassle. Smell has never come back in our W212.

FYI replacing filter alone did not cure the smell...we tried. Hence the evaporator service described above.

Send me a PM if you want to get this done or get a kit.

If you google car evaporator fungus/mold/mildew/smell you'll find all sorts of pictures of what the problem is (affects many makes & models, not just ours). However, this W212 is my first vehicle in 25 years that decided to smell like this...

mleskovar

That's the proper procedure!!

Paulcomi

FireRx Captain

Thanks to you guys, I just did this procedure to my E 350 I purchased yesterday that had the musty smell. 30 mins worth of work saved me big dollars. The Kool-It foam spray was easy to use. have a mop ready to clean the Caca that drains on the garage floor after your Done

nc211

I have 3 cars, amazon has them on sale for less than $8, I just ordered 7 cans for current and future use. I did mine in summer of 2017, held very well, but started to come back towards the end of last summer. Never got back to it before it got cold enough to not need the ac. It’s good stuff!

Aldo Muccia

Hi there - Would love to understand how to do this. I have a 2014 GL450 and the smell is unbearable.

Sumit Bhasin

Here is a great video explaining the procedure:

CopterDude

I've had this issue with a couple of MBZ. Found best way for me is take old cabin filter, cut filter off and keep just cover, spray a decent foaming cleaner (I now use FJC 5914 Foaming Evaporator Cleaner), apply to inside duct area in front of evaporator, immediately put filter cover I cut away on, and wait 15 minutes to let foam do its job. Then start the car and run ac on low for 10 minutes. I'll also take the air inlet off under the hood on my E400 and give a couple of extra shots of Lysol (pick a flavor) while cycling the vents through different positions (about a 10-second spray for each position). Turn off the car, install new cabin filter, and leave windows, sunroof, and doors open for about an hour to air out. This has always worked best for me. I did have my E400 parked for an extended period after being in TX recently and it really stunk like a dirty gym bag dipped in vinegar and cat pee (you're welcome for the mental flavoring). Gave it the above procedure and smells brand new. Hope this helps you out.

6/4/19 Update - I also will turn the car off with the upper vents open, stick the tube down as far as I can get it in the center vents and give it a shot if I notice any sign of the scent. I've done this probably 2 times in the last year and the smell has not come back. Hope this helps. The video posted a comment or 2 back is a good starting point. It's the one I originally watched to help me get started.

nc211

Yep it’s pretty straight forward actually for these cars. Pull the cabin air filter, slide the long tube up into the duct work past the filter until it can’t go any further, and release the foam. Let sit for a few minutes, look under he car and you should see nasty water dripping out the hvac drain tube, and use as normal. I’ve done it on our Toyota and the VW, same way.

S-Prihadi

That's weird. My E400 auto open its FRESH AIR VENT during engine shut down regardless of FRESH or CIRCULATE mode before engine kill.
You are talking of the Fresh Air Vent above the battery and has the special water deflection/separator box...correct ? I attached photo below...........
Could it be that I am in the tropics and my local MB program it as such ?



I been reading in this forum and wondering to why USA W212 owners can have smelly aircond issue, while I am in the tropics with very high humidity all year round which is the
recipe for disaster and yet MB owners here don't have the smelly air-cond issue, even for GLE series which I heard has a US class action law-suit for the smelly air-cond evap.

Nope, I do not have REST feature on my air-cond and prior to engine shut down, local owners do not on purpose turn compressor off and keep evap blower fan running hoping to dry the condensate on the evap.

EDIT : oops I think CopterDude refers to aircond discharge vents in the car interior ? The one for the windshield ? My bad, sorry.

Anyway, worth a check if US market cars has its FRESH air vent flap above battery box open or not during engine kill, even when mode chosen is CIRCULATE.
I think this air passage may help a bit to dry the evap from condensate.

.