[ooshnoo]

As it doesn't get very cold, I generally run my air conditioning all winter to keep down condensation and foggy windows, but lately as the temperatures been getting a little bit warmer I've noticed that the air blowing out kind of smells like my sons soccer socks after a game.

I've seen other threads where people say their air-conditioner smells like crayons, but does anyone have any experience with it smelling like feet or a similar sour smell? And if so what the hell is it? I don't recall doing it last year, so this something new.

[louielouie]

Originally Posted by Jrboulder

Change your cabin air filter.

+1 to this.

Also helps if you turn off the AC and just run the fan a bit before turning off the car.

[BrettKA7]

My car is immaculate inside, cabin air filter is new, and the temp never leaves "auto", but the HVAC still randomly smells like vinegar for about 5-10 seconds (usually a minute or so after starting the car) and a hot day brings out the crayon smell. Better than Mercedes' "normal" random rotten cheese smell, I guess....

[jmg]

Originally Posted by louielouie

+1 to this.

Also helps if you turn off the AC and just run the fan a bit before turning off the car.

This can actually promote mold and mildew growth which increases the chances of bad smelly AC if you do it too soon before you turn off your car. When you blow non-conditioned air through the vents, you are introducing relatively humid air to the interior of the air ducts. The ducts are still relatively cold from the previous use of air conditioning. As the ducts warm, they collect moisture from the warmer, humid air on the inside and condensation forms on the interior. If you leave the air on long enough, it might cause the condensation to evaporate, but if you turn the car off, the condensation remains, and you can introduce mold and mildew. Note that it takes MUCH MUCH longer for the condensation to evaporate than it did to form. You would have to turn your AC off a very long time for you to ensure that it all evaporates.

Alternatively, if you leave the AC on before you turn off the car, the air in the ducts are relatively low humidity. That means when the ducts start to get warmer, there is significantly less condensation on the inside of the ducts because the air is conditioned aka dry. Note that the condensation on the exterior of the ducts is less of a problem because even if mold and mildew grow on the exterior of the duct, our HVAC air runs through the interior, thus no smell.

So, if you had to chose between turning your AC off or leaving it on... it's almost always better to just leave it on and leave it on always. Remember, moisture is bad, and AC is basically a dehumidifier.

In the case of the OP, was there a moment you spent an extended period of time in the car without the air blowing? Were the windows closed? We generate a lot of moisture when we breath. So you could have introduced a lot of moisture if the air wasn't on. Also note that moisture from the cabin can easily make it's way into the vents. Lets say it rained one day and you got the floor mats wet. If you leave them wet in a closed door for a long time, the water evaporates and makes the air more humid. If the air isn't circulated, that moisture could make it's way to the vents and start to form mold and mildew. It's nice and dark in there.

[ooshnoo]

Originally Posted by BrettKA7

My car is immaculate inside, cabin air filter is new, and the temp never leaves "auto", but the HVAC still randomly smells like vinegar for about 5-10 seconds (usually a minute or so after starting the car) and a hot day brings out the crayon smell. Better than Mercedes' "normal" random rotten cheese smell, I guess....

Yes. That is exactly what I experience. I'll try a new filter and see if that makes a difference.

[jmg]

Originally Posted by ooshnoo

Yes. That is exactly what I experience. I'll try a new filter and see if that makes a difference.

One thing to try is to turn the heat ALL THE WAY UP and then drive on the freeway with the windows down. Get as much heat and air through your vents to dry up any moisture and kill as much mold and mildew as you can. The best time to do this is a 30 minute commute or something, the longer the better. Then IMMEDIATELY turn on the ac to get rid of all the moisture in the system. Let it run for as long as you can.

Of course, do this after a new cabin filter.

[louielouie]

Originally Posted by jmg

This can actually promote mold and mildew growth which increases the chances of bad smelly AC if you do it too soon before you turn off your car. When you blow non-conditioned air through the vents, you are introducing relatively humid air to the interior of the air ducts. The ducts are still relatively cold from the previous use of air conditioning. As the ducts warm, they collect moisture from the warmer, humid air on the inside and condensation forms on the interior. If you leave the air on long enough, it might cause the condensation to evaporate, but if you turn the car off, the condensation remains, and you can introduce mold and mildew. Note that it takes MUCH MUCH longer for the condensation to evaporate than it did to form. You would have to turn your AC off a very long time for you to ensure that it all evaporates.

Alternatively, if you leave the AC on before you turn off the car, the air in the ducts are relatively low humidity. That means when the ducts start to get warmer, there is significantly less condensation on the inside of the ducts because the air is conditioned aka dry. Note that the condensation on the exterior of the ducts is less of a problem because even if mold and mildew grow on the exterior of the duct, our HVAC air runs through the interior, thus no smell.

So, if you had to chose between turning your AC off or leaving it on... it's almost always better to just leave it on and leave it on always. Remember, moisture is bad, and AC is basically a dehumidifier.

In the case of the OP, was there a moment you spent an extended period of time in the car without the air blowing? Were the windows closed? We generate a lot of moisture when we breath. So you could have introduced a lot of moisture if the air wasn't on. Also note that moisture from the cabin can easily make it's way into the vents. Lets say it rained one day and you got the floor mats wet. If you leave them wet in a closed door for a long time, the water evaporates and makes the air more humid. If the air isn't circulated, that moisture could make it's way to the vents and start to form mold and mildew. It's nice and dark in there.

[Soul_Glo]

Anti-bacterial ac refresh might help too. Pop the can and leave ac on recirculation mode.

Normally, if I have been using ac everyday then when I turn off the car I lower the windows and naturally air it out a bit. This is better than turning the ac off and running the fan without it.

Even with a new filter you never know what crud has made it's way into the system so it is worth vacuuming it and spraying some lysol up the duct.

[ooshnoo]

Originally Posted by jmg

was there a moment you spent an extended period of time in the car without the air blowing? Were the windows closed?

Yes...for about 15 minutes last night when my kids were at soccer practice. The car wasn't even running. Once practice was done, we all got in the car, and that's when we smelled it. I thought it was their feet from their nasty soccer socks, but no...it was coming from the vents. I posted my original question right when we got home!

Also, incidentally, this morning there was no smell as the car had been in the garage all night. So maybe it definitely is the moisture from me sitting in there last night w/the car not running.

I purchased the maintenance plan which should cover the filter...just not sure if it's worth my time to save $35 by making an appointment and having the dealer replace.

Thank you for all your advice so far.

[EvenKeel]

Originally Posted by jmg

This can actually promote mold and mildew growth which increases the chances of bad smelly AC if you do it too soon before you turn off your car. When you blow non-conditioned air through the vents, you are introducing relatively humid air to the interior of the air ducts. The ducts are still relatively cold from the previous use of air conditioning. As the ducts warm, they collect moisture from the warmer, humid air on the inside and condensation forms on the interior. If you leave the air on long enough, it might cause the condensation to evaporate, but if you turn the car off, the condensation remains, and you can introduce mold and mildew. Note that it takes MUCH MUCH longer for the condensation to evaporate than it did to form. You would have to turn your AC off a very long time for you to ensure that it all evaporates.

Alternatively, if you leave the AC on before you turn off the car, the air in the ducts are relatively low humidity. That means when the ducts start to get warmer, there is significantly less condensation on the inside of the ducts because the air is conditioned aka dry. Note that the condensation on the exterior of the ducts is less of a problem because even if mold and mildew grow on the exterior of the duct, our HVAC air runs through the interior, thus no smell.

So, if you had to chose between turning your AC off or leaving it on... it's almost always better to just leave it on and leave it on always. Remember, moisture is bad, and AC is basically a dehumidifier.

In the case of the OP, was there a moment you spent an extended period of time in the car without the air blowing? Were the windows closed? We generate a lot of moisture when we breath. So you could have introduced a lot of moisture if the air wasn't on. Also note that moisture from the cabin can easily make it's way into the vents. Lets say it rained one day and you got the floor mats wet. If you leave them wet in a closed door for a long time, the water evaporates and makes the air more humid. If the air isn't circulated, that moisture could make it's way to the vents and start to form mold and mildew. It's nice and dark in there.

I'm sorry; I disagree. The smell does not emanate from the ducts; it originates from the evaporator coil.

The previous poster was correct in stating that turning the A/C off for a few minutes helps....as it takes the wetness out of the coil. The coil is always wet when the AC is running; which is why you see water droplets dripping from the car.

[jmg]

Originally Posted by EvenKeel

The smell does not emanate from the ducts; it originates from the evaporator coil.

The previous poster was correct in stating that turning the A/C off for a few minutes help....as it takes the wetness out of the coil.

The evaporator core is designed to take the heat and moisture from the air going through it. Condensation is the byproduct of its function. It is also designed to drain moisture from the coils. This is why you get a puddle of water under your car when the AC had been turned on. Unlike the Evaporator coil, however, the moisture from the ducts don't have as much drainage. Dirt and dust coupled with the humidity can increase the chance of mold and mildew grow in the ducts.

That being said, turning the AC off means that the evaporator coils are allowed to warm since refrigerant is no longer being used to cool the air passing through it. That means that the moisture on the coils no longer have a cold surface that wants the moisture. The moisture wants to go somewhere, similar to when the car is stopped and the moisture drains, but instead there is now air still passing through the coils, picking up some of the moisture results in more humid air than normal now passing through your HVAC vents. You can test this. On a hot day, turn the AC off while still driving. Look at the vent slits in the car cabin. They will get wet. That is moisture that would have drained from the evaporator case that is now trapped inside your vents.

BUT you are also right. Damage or excess dirt and debris to the evaporator coils or something hindering the drainage can cause odors. This is less preventable through proper use however, and is usually the result of debris getting past the filters or core problems. I find that proper HVAC practices are more likely to prevent odor.

[vooonoo]

.

[adhrp]

Originally Posted by ooshnoo

So maybe it definitely is the moisture from me sitting in there last night w/the car not running.

[435MSport6Speed]

I had this issue in my previous car. I used a little Lysol Orange spray in the outside air intake while the fan was on. Worked well.

[ralcala]

Hello All,

Where is the outside Air-Intake on the F30. Pictures would be very helpful

many thanks,
ralcala

[Billfitz]

Use this yearly, I do as part of my usual spring oil change routine, since you need to drop the bottom shield to get at the AC drain tube.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[vooonoo]

just saw this video. who knows if it actually works

[BK335]

Mine smelled awful too, bought a cabin air filter off Rock auto and switched it out in about 10 min.

[Billfitz]

An ozone generator doesn't rid the coils of stuff that might be growing there. By and large things that smell bad aren't healthy to have around, so periodic coil cleaning as well as a filter change is a good idea.

[vooonoo]

Originally Posted by Billfitz

An ozone generator doesn't rid the coils of stuff that might be growing there. By and large things that smell bad aren't healthy to have around, so periodic coil cleaning as well as a filter change is a good idea.

If you could make a DIY guide with pictures or a video the next time you do this in sure everyone would appreciate it

[Billfitz]

There's a video on the Amazon product page. You just have to drop the shield under the car to get at the drain, which comes out in the driveshaft tunnel. It's only ten bolts or so, but you need to have the car jacked up or on ramps to do it. You need to do that to change your oil, so it's convenient to do both at the same time.

[joemulder]

Originally Posted by Billfitz

There's a video on the Amazon product page. You just have to drop the shield under the car to get at the drain, which comes out in the driveshaft tunnel. It's only ten bolts or so, but you need to have the car jacked up or on ramps to do it. You need to do that to change your oil, so it's convenient to do both at the same time.

so you push the form backwards from the drain tube back to the evaporator ?