[MetalMK]

My car has developed a terrible smell like cow poop from the air vents. When I turn on automatic climate control, the smell comes out no matter if the AC is on or off. When I just have the climate control on (not automatic), the smell comes out for a brief moment and it won't smell anymore.

I have tried to put my nose up against the vents and it seems like only the middle vent have that smell, or it might be I can't extend my nose far enough into the vent to the left of the steering wheel because there isn't enough space.

The smell wasn't there in the summer. Right now I can have the windows open, but when winter comes I will have to use my climate control. It would be a horrible experience if I have to smell cow poop everyday.

If anyone have suggestions or possible causes of this smell, I would really appreciate it.

[GoneIn4Secs]

Maybe mold?
Did something crawl in there and die?

[DanG]

Sounds like a dead rat to me. Check the engine compartment for pest signs.

[VA Jay]

Originally Posted by DanG

Sounds like a dead rat to me. Check the engine compartment for pest signs.

I second this.

[MetalMK]

Originally Posted by GoneIn4Secs

Maybe mold?
Did something crawl in there and die?

Originally Posted by DanG

Sounds like a dead rat to me. Check the engine compartment for pest signs.

Originally Posted by VA Jay

I second this.

Thanks but engine bay looks as clean as a new car. And it does not smell like mold to me. The smell barely exists when automatic climate control is off and ventilation is on which should be the main suspicion.

[AndrewC1989]

Check air filters and refrigerant

[RAM_F30_F87]

Luckily I've never had this problem so far.
Various bimmerfest forum postings point to the evaporator as a possible source.
Here's something you might want to try:
https://1z-usa.com/klima-cleaner-air...ioner-cleaner/

[DarthFader]

If it's still under warranty get to dealer asap. Sounds like it might be the evaporator which is big $$$.

[MetalMK]

Originally Posted by RAM_F30_F87

Luckily I've never had this problem so far.
Various bimmerfest forum postings point to the evaporator as a possible source.
Here's something you might want to try:
https://1z-usa.com/klima-cleaner-air...ioner-cleaner/

Originally Posted by DarthFader

If it's still under warranty get to dealer asap. Sounds like it might be the evaporator which is big $$$.

It happens even if AC is off. I don't think air goes though evaporator when AC is off, right?

[Q_Subsub]

Check your cabin air filter? Something similar happened to me not long after I got mine and when I took the air filter out it reeked of the same smell. I swapped it out to a new one and the smell has gone away since.

[MetalMK]

Originally Posted by Q_Subsub

Check your cabin air filter? Something similar happened to me not long after I got mine and when I took the air filter out it reeked of the same smell. I swapped it out to a new one and the smell has gone away since.

Took out the cabin air filter today, I can barely smell the weird smell when it is out but I don't know if it is because of the filter or because most of air came out of footwell opening (where filter was). The filter looked really clean but I still vacuumed it and put it back in. The bad smell is still there

Btw, did your dealer replaced your cabin air filter or did you pay for it yourself?

[lower]

Try turning the recirculation on and turning the temperature up as high as it will go. Leave it like that for 10 minutes. If you've got bacteria in the system, this will dry it out and kill it.

[Q_Subsub]

Originally Posted by MetalMK

Took out the cabin air filter today, I can barely smell the weird smell when it is out but I don't know if it is because of the filter or because most of air came out of footwell opening (where filter was). The filter looked really clean but I still vacuumed it and put it back in. The bad smell is still there

Btw, did your dealer replaced your cabin air filter or did you pay for it yourself?

Sorry that it didn't get your issue resolved, although I would say if you can smell it in the filter, I would still replace it. I did it myself. It was a bit more difficult than some of the other cars I owned, with the filter going up almost vertically from the bottom and curved (if I remember correctly), but still was a pretty easy job.

[kingikra]

I had this issue in my former two Mercedes cars and now I'm starting to smell this from my M2.
In my A45 I had to go and replace the AC air filter. In my E350e I used an air refreshener bomb such as this one. I think (but not sure) that it depends where you live. For example, if you live in a hot and humid place like I do, it'll happen more often.
I haven't dealt with it in my M2 yet. Will update after I will.

[ZeroFx]

this is when you fart when the aircon recirculation is turned on

[MetalMK]

Originally Posted by ZeroFx

this is when you fart when the aircon recirculation is turned on

Very funny. Not really.

[MetalMK]

Originally Posted by lower

Try turning the recirculation on and turning the temperature up as high as it will go. Leave it like that for 10 minutes. If you've got bacteria in the system, this will dry it out and kill it.

I have been doing that for the past week, I thought it got better at first but the smell is back again. Ahhh this is annoying

[F87source]

I had this happen to me before on an older car and this is what I did to solve it (not saying that my situation is the same but I thought I could give some insight).

Ok so what happened was in the summer I would use the AC for long periods of time and not switch off the AC 10ish mins before I shut off the car or climate control. What happened was the air inside of the vents was so cold moisture condensed and when I shut off the car the moisture would just sit inside the vents without drying off (which is why turning the ac off and running ambient temp air through the vents to dry it is important). This moisture would cause mold build up causing a really foul wet dog/mold smell in the car whenever the climate control was activated. The only way I could fix it was by changing the cabin air filter, and spraying an entire can of lysol into the air ducts and blasting the fan to try and circulate it. That was the only way I could get rid of the smell.

But before you do this I suggest you check the engine bay, cabin filter, and if you have a borescope check that middle air vent for anything like a bug, or small rodent that could've died in there.

[Poochie]

Mention this to your dealer and they'll change the cabin air filter.

I'm not 100% sure but I believe it's still covered under the inclusive 3/36k maintenance agreement. If not, they go for like $30 for the OEM replacement.

I make up phantom odors or embellish about my "allergies" and get my dealer to change mines at every other oil change, as they rightfully should be doing in the first place.

Side note, I remember I had changed the cabin air filter for a friend on her Honda Accord and found remanence of a dead bird wedge in-between it. Yuck..