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Car Forum / BMW Cars / August 2005Air circulation option
My 2001 330ci has an air circulation option. One is supposedly used when the AC system is set to auto. The other is for "non" auto. I can't think of a single reason to have this switch. When re-circulation the air in the cabin, what difference does it make if the system is set to auto or non-auto? TIA > My 2001 330ci has an air circulation option. One is supposedly used when > the AC system is set to auto. The other is for "non" auto. I can't think > of a single reason to have this switch. When re-circulation the air in the > cabin, what difference does it make if the system is set to auto or > non-auto? TIA The concept is that in auto mode, the system will automatically switch to recirc when it encounters contaminated air (smoke, fumes, etc). R / John So why have a switch at all? Why not just let it be "always on" and keep the smelly stuff out? Seems to be just one more thing that can go wrong. Chris >> My 2001 330ci has an air circulation option. One is supposedly used when >> the AC system is set to auto. The other is for "non" auto. I can't think [quoted text clipped - 6 lines] > > R / John > Why not just let it be "always on" and keep the > smelly stuff out? Seems to be just one more thing that can go wrong. Perhaps that's why there is a switch? If it went wrong it might default to the setting you didn't want?  Signature*Fax is stronger than fiction * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. How does it know the outside air is bad? rtt > > My 2001 330ci has an air circulation option. One is supposedly used when > > the AC system is set to auto. The other is for "non" auto. I can't think [quoted text clipped - 6 lines] > > R / John > How does it know the outside air is bad? It just noes. Signature*Certain frogs can be frozen solid, then thawed, and survive * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > > How does it know the outside air is bad? > > It just noes. Even as far back as early E32's some BMWs have had particulate matter sensors that changed the airflow to recirc until either the incoming air was clean again or a certain number of minutes (8? 20? can't remember quite) had elapsed and the cabin air was going to be getting stale with CO2 from respiration. -Russ. Bmw's like most high priced cars have an sensor mounted in the air intkae of your heating system that sniffs the air temp and air quality and adjust your recurculating flap to open of closed for economy and quality reasons thats a good thing >>How does it know the outside air is bad? > > It just noes. In Auto, it is supposed to go to Recirc by itself if it smells foul air. You can set the system to Auto, and then manually set Recirc to ON so the system Recircs all of the time. You may want to do this when it's raining or foggy because Recirc air will be dryer than outside air, and this will help the glass to clear. > My 2001 330ci has an air circulation option. One is supposedly used when > the AC system is set to auto. The other is for "non" auto. I can't think > of a single reason to have this switch. When re-circulation the air in the > cabin, what difference does it make if the system is set to auto or > non-auto? TIA > In Auto, it is supposed to go to Recirc by itself if it smells foul air. > You can set the system to Auto, and then manually set Recirc to ON so the > system Recircs all of the time. You may want to do this when it's raining > or foggy because Recirc air will be dryer than outside air, and this will > help the glass to clear. My experience is exactly the opposite. Inside air fogs the windshield and outside air clears it off. If the AC is on, Recirc should provide drier air than pulling from the outside. If the AC is off, then the moisture in the air will simply build and build if Recirs is on, then the windows will fog even worse. Setting the Air Conditioner on is key. Some cars, not BMW, automatically set the AC on and Recirc the air when Defrost is selected. I prefer the way BMW allows us to set the life support systems however we want, but all automakers are not so thoughtful. >> In Auto, it is supposed to go to Recirc by itself if it smells foul air. >> You can set the system to Auto, and then manually set Recirc to ON so the [quoted text clipped - 4 lines] > My experience is exactly the opposite. Inside air fogs the windshield and > outside air clears it off. > If the AC is on, That's the qualifier you needed to make....because the original poster didn't distinguish between AC on or AC off. Thanks everyone. > In Auto, it is supposed to go to Recirc by itself if it smells foul air. > You can set the system to Auto, and then manually set Recirc to ON so the [quoted text clipped - 7 lines] >> the cabin, what difference does it make if the system is set to auto or >> non-auto? TIA ...so, it somehow knows a bad smell and keeps it from entering the cabin? If the answer is yes, how does it know??? > In Auto, it is supposed to go to Recirc by itself if it smells foul air. You > can set the system to Auto, and then manually set Recirc to ON so the system [quoted text clipped - 7 lines] >> cabin, what difference does it make if the system is set to auto or >> non-auto? TIA Two things, turn off the HTML (Rich Text), and I don't know how it knows that you are driving past a pasture or behind a bus. Certainly this is not rocket science though, and is a relatively simple thing to ascertain. Clean air has a certain electrical property, and if that property changes it is safe to assume that the air isn't so fresh anymore. ...so, it somehow knows a bad smell and keeps it from entering the cabin? If the answer is yes, how does it know??? > In Auto, it is supposed to go to Recirc by itself if it smells foul air. > You [quoted text clipped - 11 lines] >> cabin, what difference does it make if the system is set to auto or >> non-auto? TIA >Certainly this is not >rocket science though, and is a relatively simple thing to ascertain. Clean >air has a certain electrical property, and if that property changes it is >safe to assume that the air isn't so fresh anymore. Probably a bit like how your nose can recognize the smell of a fart in 100 milliseconds or so. The problem is making an electrical sensor/circuit that will do it. Evidently, the motor makers already did that. Now they need to develop the technology that will clearly identify the offender, open the door and push him/her out of the car. SignatureDan. >>Certainly this is not >>rocket science though, and is a relatively simple thing to ascertain. [quoted text clipped - 7 lines] > did that. Now they need to develop the technology that will clearly > identify the offender, open the door and push him/her out of the car. Or open the sunroof and launch the rockets ... > My 2001 330ci has an air circulation option. One is supposedly used when > the AC system is set to auto. The other is for "non" auto. I can't > think of a single reason to have this switch. Think you've misunderstood the meaning. Auto recirc has no link to auto on the climate control - it simply defaults to fresh air, but changes to recirc if it detects noisome air. It explains this in the driver's handbook. Signature*Stable Relationships Are For Horses. * Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. |
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