thefisch

did you spray any in your air box or clean it out while you had it off? I suppose moisture, dirt, etc. could collect there also.

ArcticE

Yes, I cleaned and sprayed the airbox and mesh grill at the base of the windshield just incase. They were both pretty clean but couldn't hurt.

thefisch

Inspired by ArticE, I decided to try this today. First I removed the air box under the hood and inspected the intake and blower sides (all pre filter). There was definitely some pollen residue which could be due to the recent pollen season (heck in FL it seems year round). But there was no odor in the air box. I sprayed it to clean it out just in case. Doing this allowed me to see that the drain in the air box was working which is a good thing to keep in dry in there.

Next I removed the cabin air filter using the DIY instructions found here. On a side note, the little metal clips were missing on my car (it's used). Only the plastic slider and filter seal keeps it in place. But the seal seems good enough and not having to fuss with the metal clips makes the install easier. The intake side of the cabin filter was not as white as the outflow side as you would expect from a little over a year of use (supposedly replace during last B service by previous owner according the MB records). There was no odor to the filter itself which leads me to think the odor source in my car is after the filter at the evaporator coils.

While I had the filter out, I took some video with my GS3 up in the air filter housing so I could inspect the condition of the housing pre and post filter. Prefilter you could see some pollen residue between the blower and the filter (towards the passenger side) like there was in the air box. After the filter (towards driver side) the housing looked clean as it should be. Unfortunately the curve to the housing would not let me see any part of the evaporator on the post filter side. Too bad I don't have one of those fiber optic spy cameras.

I ran the system without the filter in place in hopes that I could spray Lysol into the post filter side to avoid saturating the filter and trying getting as much as possible to the coils. Unfortunately, without the seal of the filter in place, the air from the blower just comes out the filter opening as you'd expect.

Next, I opened all the glass, ran fan on high with temp LO with no AC and sprayed Lysol into the blower fan. I would spray Lysol for 15-30 seconds and then it run for about 5 minutes. Then I changed the vent mode and repeated until all 3 modes were used (I know there are 5 modes but I used just the 3 main ones). Then I jacked up the heat to HI (to be sure it went through the heat exchanger) and repeated the cycling with all the modes again. Then I repeated all these steps with the air recirc on and sprayed Lysol in the passenger footwell area so it could be brought it that way. Then I repeated all these steps (LO, HI, recirc and three vent modes) with the AC on. I just wanted to be sure all the dampers and ductwork got some Lysol.

Afterwards, I drove around for about 15 minutes to air out the car while alternating using the system with glass open and then shut and with and without AC. Since I can still smell Lysol, it's too early to declare victory. But at least it smells better for now.

On a side note, I am sure MB has a good reason, but I have seen other cars where the cabin air filter is between the blower and the outside air, not after the blower. That setup would allow you to spray Lysol into the blower and get most of it to the coils as you are not saturating the filter. But maybe it is better this way for a good reason.

For those of you who saw my thread on plugging my tire, yes I did do something stupid with this DIY project. During my initial inspections, I ran the fan on battery alone for too long and had to jump start the car. Battery seems fine now. The streak continues.

ArcticE

Update:

Lysol smell is gone and there is still no trace of the foul odor when using the AC. Very happy with the reaults.

thefisch

Glad to hear it. Mine has been good most of the time. As suggested, I have been trying to turn off the AC using the button a few minutes from my destination and still running the system to dry it out. I was surprised that the HVAC still blows cold air for a few minutes afterwards. While it is inconvenient to not just it the AC on, at least it is not unpleasantly warm to turn it off early.

I have only noticed an HVAC odor a few times since the procedure. Once out of a dozen of more times when starting my car with the HVAC coming on right away (normally I leave it on when shutting off car). And a couple of times while first engaging the AC (after driving with HVAC on and AC off and needing to cool it down). The latter example doesn't make sense to me why the odor would begin when engaging the AC after the HVAC has already been going with no odor until that point. The only thing I could think of was that the HVAC system went into recirc mode on its own when I turned AC on and the odor came from the recirc intake area. I haven't been able to replicate it in any consistent manner.

Thankfully, it has been mostly odor free.

mleskovar

Why not? It's a refrigerator. It takes time to warm up the coils/tubing just as it takes time to cool them off. That's why the ECO 'feature' doesn't blow hot when the engine stops for short amounts of time.


Recirc ONLY shuts off the air intake entering the car from the vent before the cabin fan. It recirculates the air already in the cabin space.

One thing that should be considered by those with this problem....usually high humidity locations.....is that mold has blocked the drain tube. Even if you see water dropping beneath the car the tube could still be blocked and only releasing water after it builds up enough to overcome the blockage but still keeping enough in the system to grow more mold.

thefisch

It stayed cooler longer than I expected based on experiences from past cars which typically would get a little warmer and muggy in less than a minute. My car doesn't have the ECO feature.


How do you check the drain tube?

mleskovar

I was just using that as an example of how it takes more than a couple of minutes for the evaporator to heat up. You still have the same HVAC system.

Not easy unless you have a diagram. It should exit at the low point of the HVAC enclosure. When you stop it should drip from that tube. Sometimes there's stuff/parts it drips over so you have to look for it. Ideally you could pour water in the enclosure....like when the filter is removed...and it should just pour out the tube. I don't know if there's any valves to regulate it or not. Does anyone know the path for sure?

ArcticE

I would also like to know where the water drain is so I can check it out and make sure it isn't blocked. Does anybody have any pics or a diagram that would help out?

konigstiger

Evaporator (left 170, right 160 in diagram) – hoses are routed beside transmission - interior access without disconnecting (i.e.: squeeze out any debris if need be) need to remove flooring covering.

Sunroof front left/right 600, rear left/right 700
Panoramic front left/right 510

Engine compartment cowl left 220, right 230

ArcticE

Wow thanks konigstiger! I think this thread will be helpful for a lot of members now with the smell problem. Going to check the drain on my car later to make sure its clear.

thefisch

Thanks konigstiger! Here are some photos I took of the hose on the passenger side after removing the underdash panel to access the air filter and folding down the carpet panels. One is an overview and the others are close ups of the attachment point at top and bottom.

The hose appears to have an inner skeleton with ridges about every two inches. I suppose that is needed to maintain the integrity of the hose since the hose material is very soft, easy to squeeze. There were no noticeable obstructions when pressing between the ridges. It also looks like you could slide the hose off the upper attachments if you wanted to check further.

Looking just underneath the housing, I could see the hose on the driver's side. The carpet panels didn't appear as ease to move out of the way so I didn't venture further.

thefisch

As you can see from the diagram posted by konigstiger, the cabin air filter sits in the housing between the blower and the coils. Here are some pics from the inside of the housing on my car to help you visualize it. Sorry for the quality but these are screengrabs from video taken while holding cell phone in the filter housing.

Blower side (pollen visible from before cleaning):
View from filter towards blower -

View of blower from further in -


Evaporator side (video taken after cleaning):
View from filter towards evap -

View further in where you can first see coils -


Another view of coils -

Close up of coils -


As you can see, you could easily reach the coils with a cleaner from the opening in the filter housing where the cabin filter goes in. The coils on my car seemed clean enough for me to just wait and see if the odor returns. If I need to apply Lysol again I may just spray towards the coils from filter opening to avoid saturating the filter and the blower.

BeachBunny

Big thanks to both konigstiger and thefisch!!!

Boss just had his wife drop off her 2003 C320 (fully loaded, complete with separate AC blower in the rear seats) with an absolutely vile smell from the AC. Using the diagrams and photos, I was able to get access to the evaporator and soaked it in Lysol for awhile...

Currently have the car sitting behind the office building with our ozone generator cranking away @ full throttle. If it's good enough to clean the smell of dead bodies & fires from apartment buildings, a little mold on the evap should be a piece of cake.

SnakeDoctor

I have to try and check the drain tube(s), because my car is still new, and has had the smell from about 4K miles. I've tried spraying lysol in the system, and it helps, but doesn't get rid of the smell. So silly no other car I've owned had this issue, but both of my MBs have. Add wiper chatter to that too. It's a good thing that I absolutely love everything else about the car.

thefisch

While I have yet to remove the drain tubes (figure I will mess something up), I have noticed drainage on the ground from time to time. My other car (Honda) drains constantly, but my MB seems to drain when it pleases - usually after it is parked for a while.

I gave up on turning off the AC before reaching the destination - too much fuss and there would be the occasional odd smell as I mentioned above. I did have the air filter changed since it was offered to me at no cost by Carmax when I complained about the smell. With a new filter and lysol treatment, there have been no smells for three months and I run the AC all the time (you have to here in Florida).

SnakeDoctor

Yeah, when I get the filter changed, the smell goes away for a while. But, my new car is...well, new! It shouldn't have a smell already :/ I live in Houston, so I suffer from the heat and humidity, but again, my other cars don't and didn't suffer from this problem. And I'm talking over the span of years. With the MBs, I'm talking about time-frames of months.

thefisch

Hope that doesn't mean mine will come back. Like you, I haven't had this issue with other cars in the heat and humidity of the South. Common sense would tell us that if removing the filter improves the smell then that must be the cause. Or else the smell would persist even after the filter change.

I read an opinion somewhere that the system is so tightly sealed on these cars that the air is trapped which leads to the air filter absorbing more odor. At the time, it seemed like a sales pitch to justify selling more filters. But after living with that smell, I don't mind a DIY filter change for $30 if that makes it disappear for 6 months to a year. Although, it shouldn't be that way...

SnakeDoctor

I tried taking off the box thing under the hood (sorry I don't know what it's called), and I could see a spinning fan. I sprayed a lot of lysol in there with the system running and no AC, as well as with AC on. I ran recirculation mode and sprayed in the footwells. The smell was still there in the morning. I suppose it should be noted, I only smell something when the car first turns on, after that, it's gone.

So I guess the smell must be coming from somewhere else in the system that I didn't get the Lysol to.

Live Oak

Well, I am only slightly qualified to respond to this thread, but I experienced the problem once --- after a dud tech (no longer employed) programmed the drying fan function OFF.

It's important that the drying fan runs about an hour after the car is shut down, and runs for about 45 minutes (or whatever). You can hear it quietly running out in the garage. The whole idea is to dry out the evaporator so nasty stuff won't grow there.

I WONDER, if in the case of people who for some reason turn their AC off just before stopping the car, they are sending a signal to the computer "The AC wasn't running, no need to turn on the dryer fan." I say I WONDER, because I've never tested it.

I understand "The Florida Problem" --- I'm sure nobody in Germany has ever experienced heat and humidity like that, and maybe that's exactly the problem in the 212 design. OTOH, MB sells cars in South and Central America and Africa.

BUT, if I were experiencing the smelly problem, I would make damn sure the dryer fan is running every time the car is parked. And if not, squawk the problem to the dealer.

thefisch

Next time I bring in my car for service, I am going to ask about the setting on the drying fan. My fan does not run after the car is off regardless of the climate control setting before switching car off. I have checked several times on that and would have noticed. Downside of the fan running for me would be battery drain, I've had to jump the car twice in four months due to accessory use when off. Still starts up fine.

Live Oak

My whole history with this started with a battery drain to 0. It turned out to be a service notice about some other fan running all night. It required a software update, but in the process the tech (now probably a service station attendant) also turned off the drying fan.

The drying fan waits about 45 mins to an hour before starting up -- probably to let any evaporator ice melt and drain on the garage floor. Then it starts drying for 45 mins or an hour, from my experience.

It's a very quiet fan --- probably not much battery drain.

I'm no expert, but if that fan doesn't run, then I'd say trouble is brewing. We had the smell problem here in the desert, where humidity is typically in single digits.

belarus27

started having this issue about 2 weeks ago , now i know what you all mean by *smelly feet* lol
gonna try to fix it his weekend , and gonna order a new cabin filter as well.
2010 550 93k miles

thefisch

A new filter worked for me last time. However, after 18 months (basically during the second summer) it started to smell again. Same thing - a blast of warm musty air at startup but then it dissipates.

Since I am only a few months away from another filter change, I thought I would experiment a little more. Over the weekend, I pulled the filter and lysoled both sides of it and sprayed a little in the filter housing opening. Left it to dry overnight and today there was no musty smell that I noticed (barely a hint of Lysol). Will see how long this lasts.

belarus27

never changed my cabin filter since i bought the car (i know i know... im bad , but thats smth i never really paid enough attention to ) so ima order one soon off ebay... but before it comes in ima buy a lysol can and disinfect it before i put in the new one in that way ill be on the safe side.
thanks for your input broski lol you always help out if you can. appreciate it. keep me posted if u get any smell back. and you sprayed it under the hood on the passenger side where the blower at i guess.. right?