Hello,

Sorry for the long post. I have a 2009 CLK350 Cabriolet that has had the well known moldy AC smell issue since I purchased it new. It smells the worst when the A/C is not running and the car has been sitting at least a few hours. With the A/C running the smell is very minimal. I've heard this is because the fan is blowing. When I first open the doors in the morning the interior smells of nothing but strong mold. I have had the dealer clean the evaporator but the smell was only reduced a small amount. I started researching online and tried a variety of things:

Ozone generator: this removed the odor but it immediately comes back once the air is run a short period of time (1-2 hours).
Replaced filter located above the battery under the hood and both cabin filters below the glove box. No change or improvement at all.
Removed the exterior filter above battery and sprayed a can of Lysol into the blower fan. This helped but did not completely remove the smell and the smell quickly returns (1-2 days)
Sprayed Frigi-Fresh then switched to the Mercedes OEM cleaner, then lastly Nextzett Klima-Cleaner (2 bottles) by removing the cabin filters below the glove box and spraying directly into the area where the evaporator is to the left of the filters. The foam turns to liquid and immediately drains out of the drain hole between the engine/trans under the car so I know the drain is not blocked. The Nextzett completely removed the mold smell and the air is actually cooler too. But this lasted 1-2 days and after the air has run a day or two the mold smell comes back with a vengeance. Since the smell can be eliminated temporarily I tend to think the vents are not contaminated enough to cause the smell to return and that the source is the evaporator. If I don't run the air after using the Nextzett the smell does not return. It's only when I start using the A/C again.

I am beginning to believe after trying all of these things that the evaporator is designed poorly and does not allow the condensate to evaporate/drain quickly enough, so mold quickly begins to form within 24-48 hours again. I found various information about this in various forums and learned from a Mercedes Star bulletin that the 2009 (based on VIN) has the newer anti-microbial evaporator which Mercedes started putting in the CLKs to try and address this. But it does not seem to help much if at all. I am in the hot and humid southeast USA and have owned other Mercedes models (2006 E350, 1997 C230) and other German and American cars and even with our humid climate I have never had this problem! Ever. Has anyone identified an evaporator that can be purchased separately and installed perhaps by an indy shop that will eliminate this problem? I know it's a massive job and pricy but the car only has 30,000 miles on it and I paid $67,000 for it when new.

Thank you!

 

Yup you definitely have a mold growth. Never had this on any MB except my wife’s 2015 ML350. I used this product in the link below a couple of times and it went away. It may take about 3 or 4 cans of this but I can assure you it works.

 

You may not want to hear this, so…here it goes!

Sell the car, trade it in, basically get rid of the car for something to your taste and price range and never look back. If there is a problem that is designed/ engineered into the car (unintentionally) that is unable to be rectified then sell it.

 

Or just buy some cans of Kool-it for a lot less and it will correct the issue before jumping to the point of trading/selling it lol

 

Thanks, I forgot to mention in my original post that I had tried 2 cans of Kool-It along with the Nexzett and the OEM cleaner. The smell went away for a day or two then started coming back again. I think I will just have to live with it as the odor keeps coming back.

 

Drain lines are cleared? The ones from the sunroof? Keep it up with the Kool-it for a little longer. The goal is to disinfect the evaporator and the make sure there is no water build up in there. This is why it must drain correctly. Kool it should be installed from under the car into the drain hose and sent all the way up. Another thing you could do is about 1 mile before your destination turn the AC button off that way it will help evaporate any excess water in there to dry it out. Like I said no issue with my CLK so I can’t help

 

Thanks for the ideas: yes, the drain lines are clear because whenever I used the evaporator cleaner (applied to left area of cabin filters under the glove box - 2 cans of Nextzett, one can of OEM, 2 cans of Kool-it so far) it comes pouring out underneath the car between the engine and transmission. And regular condensate drains out normally there too. There is no drain hose, just a hole somewhere up between the engine/transmission. I can crawl under there and see if I can get the Kool-it plastic hose to reach it. The car is a convertible so there are no sunroof drain lines. Not sure if the convertible has drain channels that could block like other cars I've had. I'll check that. No leaking or wet spots inside the car at all anywhere.

I tried an interesting test the other day: I used the last can of Nextzett and normally the car smells when it sits for several days. But it never does after using a can of the evaporator cleaner if I haven't driven it since the cleaning. But once I would drive on my commute the next morning the smell always comes back. But as a test I didn't turn on the A/C during my 20 mile commute and just ran the fan, assuming there wouldn't be any condensate created that could mold up in a day or two. After letting the car sit a couple of days I opened the door and that nasty smell was back! I guess the evaporator just isn't fully cleaned and air flowing across it brings the odor into the cabin again? I also have tried the "turn off AC 1 mile prior" several times and turning up the heater to high and driving it for 30 mins but neither helped. I will try to find an indy shop who has dealt with this and see if they can do a more thorough cleaning. It is good to know that you have a CLK and do not have this problem. That tells me there may be hope. Or maybe this problem is not just the evaporator?