| Originally posted by Dirty_Tool@Jul 25 2004, 05:54 PM |
oooohhhh, enlighten us on stinky A.C please!!!
You play dirty, Mr. D-Tool!
Why some A/C system goes "stinky"
Stinky, or as my kids refer to as 'socky', odour is caused by fungi living on your evaporator core.
This fungi thrives in warm moist environment (like inside of your shoes). Ever wonder whay stinky A/C smells like sock that has not been washed for a while?
When you turn on A/C in hot weather, for faster cabin cooling the climate system or the user selects 'Recirculate' mode or 'MAX A/C' mode. MAX A/C actually puts the climate control system in recirculate mode.
Recirculate mode closes the door that allows fresh air into the car. Where does the air supply come from? From inside the cabin! So what you are doing is recycling the stale air inside the car over and over. However, in doing so, you are taking the same air and circulating it through the evaporator core (the heat exchanger that cools the air) over and over to achive faster cooling.
Now, you are only supposed to use recirculate mode for about 10~15 minutes until the cabin is at comfortable temperature. Then you should select regular A/C mode to allow fresh air in.
After a while, does your feet feel somewhat comfortable? A/C must be doing its job of getting some cool air into your shoes (if you wearing one). What would happen to fungus that loves to make that odour in your shoes. You have circulated it all over the car. Now, whether you use fresh air mode or recirculate mode, you cannot avoid this. Eventually, some of this fungus would make its way into the A/C system. So that's the major source of the 'socky' fungus.
How does it grow? The evaporator core inside the A/C system cools the air moving through it. Air warm moist air passes through the evaporator core, the temperature drops. Say the incoming air is about 30°C (about 80°F). The outgoing air from evaporator would be about 5°C (about 40°F). The air at 5°C cannot hold as much moisture as the air at 30° so it must release it as DEW on to evaporator fin surface. So the water collects on the surface of evaporator. This is discharged through a drain as long as blower motor is moving the air through evap core.
So you say evaporator is self cleaning? Why yes, it is! That is, if you use it properly. When you arrive at your destination, what do you do with your A/C system? Do you just shut it off? I think most people do. Evaporator is not complete dry! It is still wet! Then you leave the car in hot sun for hours for 'socky' fungus to manifest and nurture its young! The fungus will, given time and repetition, attach itself to the evaporator. Then, whenever the climate is most (hot humid days), when you get into the car, you immediately smell what seems to be old laundry. Mystery solved.
The smell is caused by personal hygiene, nature, and poor A/C knowledge. So how do we overcome this?
Forget personal hygiene. Let yourself go. You cannot avoid this.
Forget nature. It gets hot in summer. What can you do. Move to outer space?
So that leaves A/C knowledge. But before we get to that, I'll describe what is sometimes done to the evaporator to reduce the odour. Most evaporators (at least the ones used by our company) have fungicide or anti-bacterial coating as well as coatings and designs to flush out the water as easily as possible, ie. make the environment as unhabitable to the fungus/bacteria as possible. So solutions are there but nothing lasts forever. The coating/fungicide/biocide will eventually become ineffective by repeated usage and crud that accumulates on evaporator surface (dust, hair, oil, you name it).
The fun part. What can you do to prevent/reduce the odour? Follow these simple steps.
1. Turn OFF your A/C about 3 minutes before you arrive but keep the blower in highest setting. This dries your evaporator. Use recirculate mode as this recirculates cooler, drier air inside > which will dry the evaporator faster that fresh (?) outside air.
That's it. The point is to dry the evaporator core (which is full of moisture) and bring it above DEW POINT, ie. about same temperature as ambient. That's all you need to do every time you turn the engine off.
If you A/C already smells foul, you cannot completely get rid of all of your fungus. You can replace/clean your evaporator core + A/C case but that gets pretty expensive. However, if you keep your system dry when the engine is off, I am certain that the odour level can be reduced. After all, fungus cannot grow where there is no moisture . . .