Does anyone have the same problem when turning on the AC? It's usually on rainy days or when it's cold outside when the smell is stronger! I only have 48k on the car and done maintenance regularly.

TONS of people have this problem. It is common on many cars. It is extremely common on Mercedes and has been for at least a decade. They just can't quite figure out how to build an AC system that stays odor free in all climates.

Are you under warranty? Dealer will clean it free, but often the problem will come back every few months.

First run it with the AC off and set on max heat (when the engine is hot) through all vents for 10 mins. Then run it for 10 mins on max cold with AC on.

If you use your A/C a lot it is best to run the vents on heat for about 30 seconds when you are done with the A/C. If you shut the A/C off it leaves condensation in the vent tubing. This eventually leads to build up of mildew. Running the heater for a few, when finished, will dry the tubing up, and prevent the problem.

My 2008 just had it's 4th birthday and has never had the stink you mention because I always leave the AC on automatic.

I won't beat a dead horse by debating whether use Auto all the time or not (you hear that Sportstick? do not chime in! )

If the dealer won't cover under warranty, just get a can of 1Z Klima Cleaner. Works very well and removes the source of the ordor vs just masking it.

Good evening, all. How is everyone? Fine day here, brisk, but sunny. Going out for a drive now. Wonder what the A/C will do, as it's set on..............

My W203 stunk so bad that 2 bottles of 1Z properly applied lasted for about a week and then the smell came back full force.

I live in a humid climate.

I turn my AC off 5 min before arriving home.( a habit,at the same place).

It allows evaporator to dry out

No smells from A/C.

Simple.

Change your cabin filter.

Shut A/C 5 miutes before stopping and change your cabin filter.

Saludos

When you guys say 'shut your AC 5 minutes before stopping' do you mean you press the AC button to turn it off and leave the fan on? Or do you turn the AC button off, then turn the entire system off and back on?

In the W203 and W204 when you press the AC button to turn the AC off, it does not actually turn off. It seems to stay on indefinitely, but running at a much lower level. There is also a noticeable "whirring" noise from the valves in the compressor when it is running at this low level and the engine is revving at low RPMs. The only way to truly turn the compressor off is to turn the entire system off and back on. I've even seen it written in MBs own documentation. It's very annoying.

If you run the vents on heat for about 30 seconds when you are done with the A/C, then you ensure the AC os off.

So, 2-3 mins out. hit AC off button......raise thermostat to 90+ and let it blow. When you are home, simply turn it off.

The idea is to dry out the coils and evaporator prior to letting the vehicle sit.

This still leaves the compressor on a low setting usually (varies by humidity which is sensed). It probably works either way though since the heat still pulls the moisture away. It would work better if the AC was forced fully off first.

I joked earlier after Doanster expressed reasonable impatience at listening to me on this topic again. So, let me ask a different question. Does anyone here really think that after all the design and development by the HVAC engineers, who clearly assume AUTO mode will be used in all but unusual/exceptional conditions, that one needs to go through all these machinations (turn it on/turn it off/how many miles/minutes to home/how hot is it? OMG! ) to keep their system working free of bad smells!?!?! Make your lives simple, folks!! Just use it the way it was designed to be used!

Sorry, Doanster....I held off as long as I could stand it.

I'm better now.

I completely agree. The "just turn off your AC 5 minutes before you get home" answer is bull. Not only is that a completely unacceptable answer, but even if it were, I'm not going to remember to turn the AC off 5 minutes before getting to my destination. I'm not directing this at those of you who posted that solution - it is a good solution given the circumstances. It's just a load of crap that we have to resort to that due to MBs lack of proper engineering.

En Garde!! :-) Of course Auto would prevent the smells... that's because the compressor always runs!
That's the only reason I continue to be stubborn about this. There is just no reason to use the A/C that much up here in the NW. I actually use it more in the winter due to the rains vs the summer heat. If engines wouldn't bog because of the compressor being on or MPG going down because of it, I wouldn't care and indeed use Auto. But alas...

Acr - why would it be BS to turn off the AC five minutes prior? If you search for threads on this, I've mentioned that Volvo has the true solution here. Twenty minutes after the car has been running the AC, it turns the fans to high for ten minutes to dry out the system. This is on its own, after you lock up!

Why would auto prevent the smell with the compressor always running? Always running would = more smell.

Volvo isn't the only one who runs the fan after leaving the car. Mercedes also does this on our cars. I'm not sure if all W204 do it or just 2012 on, but I did see the documentation explaining how it works. The fan runs at the lowest setting to dry out the system. The PDF is floating around this forum somewhere.

It's BS to turn the AC off for five minutes prior because that is not an acceptable solution. I'm not going to remember "oh I'll be at XXX location in 5, better turn the AC off nor do I want to sit in a hot car for 5 minutes when it's over 100 degrees out during the summer. Like I said, it IS a good solution on our end given the problem at hand, but its BS that we should have to resort to said solution.

Having the system engaged dries out the air being sent to the cabin, preventing the conditions which allow the offensive-smelling mold to grow. AUTO is the 1) intended, and 2) easiest method to manage this issue, once your system has been thoroughly cleaned. For your next car, start this way from new, and as with RLE and my cars, three+ years in, no problems!

I'm confused. When he said auto I thought he meant with the AC on which is why I was saying the compressor would run and create more water. Auto *with the AC off* would certainly help dry the system out.

I've only had to run the AC a couple times in the 2012 - winter is almost here. I plan on leaving it in Auto all summer long with the AC on. If things start to stink the dealer can clean it every month until they are blue in the face. It's a lease

There is no distinction between AUTO and A/C on. When you set it to AUTO, and select a temperature on the dial, the system decides when to turn the A/C on or off to achieve the desired temperature. (It likely also has a program for periodic compressor activity to maintain system dryness.) You don't manually turn the A/C on or off. This is a "set it and forget it " system for the majority of conditions. Leave it in AUTO for as long as you own it, just choose the temp, or manually override for unusual defrosting situations, and then, return to AUTO. It really works very well on its own!

No argument about this being set-it and forget it along with it not generating mold/smells. My problem is that I don't need the AC to run for a majority of the year, so I only manually use it when needed, for the primary reason mentioned above - engine bog. Very evident w/ 6spds because you have to rev higher when the compressor is running.

HOWEVER, perhaps I haven't given the system/logic a chance to prove itself, Sportstick? Whenever I see the AC button lit, I assume the compressor's running. Yes, I know that it will periodically take "breaks", but I thought those were far and few between. The weather is perfect right now so to speak. Not too hot, not to cold, and dry. When it begins to get colder with more rain, I shall bite the bullet and use full Auto for a while and see if I like it or not.

Acr - my point/argument about always running the compressor (whether all the time or intermittently), wat that it dumps more refrigerant into the system, thereby not allowing any mold to form... it's always going. Have you noticed that on cars that already smell, once you turn on the AC, the smell goes away? I'm glad that you say MB has implemented the after-blow feature. That would take care of the issue regardless of whether you use Auto or not.

The whole reason you get this smell is because of the condensation forming on the fins of the coil. This is normally where the mold grows. Not using the AC should mean no smell. This is why running the system without AC for the last 5 minutes of a drive is the recommended 'solution'. It dries the water that the AC generated out.

I completely understand how the system works and that set it and forget it is the expected / proper way of using it. I'm just saying that AC off would make more sense if someone was worried about mold. You think that people are getting the stink because they mess with the settings too much and turn the compressor off? If so what is the logic for that?

As far as system dryness - you mean keeping the air in the cabin dry to prevent fog on the windows? The system does this through a humidity sensor within the HVAC ductwork - it tells the compressor to run when there is too much humidity.

Sorry, something's apparently just not coming across correctly on my part. Regardless, I think we all understand how the system works, how the smell happens, etc. The three of us have hijacked the OPs thread. We should just leave him/her with: "Get the system cleaned, then hit the Auto button from now on or else!" (I'll refrain from adding anything else to the end of that. )

Amen ! To each his own. I think Rexi has the message !!