what's with the air recirculate scheme?
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Member
Joined: Nov 2009
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From: austin, texas, usa
2006 e320 cdi
what's with the air recirculate scheme?
The AC sometimes gets a little too cold, so I turn off AC and turn on air recirculation. It stays on for a few minutes, usually less than 10, then, turns itself off. And all of a sudden, I've got a puff of warm air comes into the cabin. What's the deal with that? I've only read about automatic turning on of recirculation, but not turning off. Does anyone know why? Thanks!
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From: Southwest USA
Another round of ICE
The AC sometimes gets a little too cold, so I turn off AC and turn on air recirculation. It stays on for a few minutes, usually less than 10, then, turns itself off. And all of a sudden, I've got a puff of warm air comes into the cabin. What's the deal with that? I've only read about automatic turning on of recirculation, but not turning off. Does anyone know why? Thanks!
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Joined: Apr 2006
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From: Barrington IL
2015 E 250, 1999 BMW M Roadster, 1939 International Harvester, 2023 GLC
recirc
If you hold the recirc button it will close all windows and sun roof. It does this to make it easy if you are in a tunnel or a dusty place. One button does it all.
Kind of nice aye
Kind of nice aye
Senior Member
Joined: Feb 2010
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From: Cross Roads, PA
2008 ML320CDI
When it auto mode it will switch from fresh to recirc or blend the two without you touching anything. Turning off the AC is in fact the wrong approach, as sportstick stated, just turn up the temp or lower the fan speed. If it continues to get too cold, you might need a new evap temp sensor.
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From: RI
2017 S550 4matic
I must admit I do not understand your approach. If the A/C gets too cold, why not just raise the temperature dial to a comfortable level? The recirculation function is used to cool the compartment faster by taking already cool air in the cabin and re-cooling it further instead of the task of trying to cool outside air. This is what happens if you use the MAX COOL function. It is not meant as an ongoing setting, but rather a temporary assist (it also works if passing through a dusty area or behind a smelly truck to minimize outside air blend). It should not be kept on for long periods, as you are increasingly breathing the same recycled air versus bringing in fresh air.
When it auto mode it will switch from fresh to recirc or blend the two without you touching anything. Turning off the AC is in fact the wrong approach, as sportstick stated, just turn up the temp or lower the fan speed. If it continues to get too cold, you might need a new evap temp sensor.
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From: Southwest USA
Another round of ICE
So, we agree that neither of us claim it is unfiltered! No need to hesitate! The gaseous composition of recycled air is different and less desirable than fresh, and at some times of the year will lead to fogging of windows due to excess humidity from human sources. The OP's issue is best addressed by simply adjusting the temperature control and leaving the recirculation feature alone, unless dealing with need for rapid cooldown or in an adverse exterior environmentl, both temporary conditions.
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Senior Member
Joined: Aug 2011
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From: RI
2017 S550 4matic
So, we agree that neither of us claim it is unfiltered! No need to hesitate! The gaseous composition of recycled air is different and less desirable than fresh, and at some times of the year will lead to fogging of windows due to excess humidity from human sources. The OP's issue is best addressed by simply adjusting the temperature control and leaving the recirculation feature alone, unless dealing with need for rapid cooldown or in an adverse exterior environmentl, both temporary conditions.
yes, however in terms of doing so with the AC on, the air passes through a condenser/drier system anyway thus eliminating that which you refer to as 'excess humidity from human sources'.
So, in effect, we're both "kind of right". The recirc, however, is the number one way to increase your a/c system's efficiency. Couple the activated charcoal with the drier and I don't think you'd see much difference in air quality from filtered fresh air.
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04 E320 4M Wagon
The recirc is turned off automatically to protect the driver from getting asleep due to the low oxygen level. This is written in Owners Manual
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Tesla Model S P100D
Just out of curiosity: are you saying that the oxygen content is the same in fresh air and in the air that is going to be in the car with an alive (breathing) driver with a Recirc on?
The recirc is turned off automatically to protect the driver from getting asleep due to the low oxygen level. This is written in Owners Manual
The recirc is turned off automatically to protect the driver from getting asleep due to the low oxygen level. This is written in Owners Manual
Also people should use the automatic climate control systems available in our cars. A lot of thought has gone into them with temperature and even sunlight sensors. Just set the desired temperature and leave it on auto. Unless I am mistaken, there is a sensor that detected if the air outside is bad and automatically switches the car to recirculate air for a short while.
Senior Member
Joined: Aug 2011
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From: RI
2017 S550 4matic
As it should be. Unless the air outside is bad or it is a very hot day and you are trying to cool the car, it is not a good idea to drive around with the climate controls set to recirculate air. No amount of scrubbing or filtering the air can restore the levels of carbon dioxide that will build up as oxygen gets depleted.
Also people should use the automatic climate control systems available in our cars. A lot of thought has gone into them with temperature and even sunlight sensors. Just set the desired temperature and leave it on auto. Unless I am mistaken, there is a sensor that detected if the air outside is bad and automatically switches the car to recirculate air for a short while.
Also people should use the automatic climate control systems available in our cars. A lot of thought has gone into them with temperature and even sunlight sensors. Just set the desired temperature and leave it on auto. Unless I am mistaken, there is a sensor that detected if the air outside is bad and automatically switches the car to recirculate air for a short while.
NO recirc system on any car ever completely seals off the outside air. SOME outside air ALWAYS gets in, regardless of the car. Why do luxury cars seem to be better? Because ALL the air going into the cabin goes through the cabin filter.
The recirc may be on a timer, that's one thing. But I (at 6'2" and 240lbs) certainly put out more Co2 than a 5'4" female that weighs 90lbs. So while the recirc shutoff (if it even works the way you say it does) may correct the air quality for her, what happens when my much higher Co2 output overruns that?
This discussion is in the weeds as far as what the OP posted...I'm shocked we're talking about oxygen contents in a conversation about an HVAC setting in our cars...
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From: Southwest USA
Another round of ICE
you guys honestly believe that mercedes engineers would allow the recirc option to seal you into a CO2 cabin of doom? Seriously?!
NO recirc system on any car ever completely seals off the outside air. SOME outside air ALWAYS gets in, regardless of the car. Why do luxury cars seem to be better? Because ALL the air going into the cabin goes through the cabin filter.
The recirc may be on a timer, that's one thing. But I (at 6'2" and 240lbs) certainly put out more Co2 than a 5'4" female that weighs 90lbs. So while the recirc shutoff (if it even works the way you say it does) may correct the air quality for her, what happens when my much higher Co2 output overruns that?
This discussion is in the weeds as far as what the OP posted...I'm shocked we're talking about oxygen contents in a conversation about an HVAC setting in our cars...
NO recirc system on any car ever completely seals off the outside air. SOME outside air ALWAYS gets in, regardless of the car. Why do luxury cars seem to be better? Because ALL the air going into the cabin goes through the cabin filter.
The recirc may be on a timer, that's one thing. But I (at 6'2" and 240lbs) certainly put out more Co2 than a 5'4" female that weighs 90lbs. So while the recirc shutoff (if it even works the way you say it does) may correct the air quality for her, what happens when my much higher Co2 output overruns that?
This discussion is in the weeds as far as what the OP posted...I'm shocked we're talking about oxygen contents in a conversation about an HVAC setting in our cars...
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From: RI
2017 S550 4matic
Perhaps you are employing the old debate tactic of taking the other side's position to the extreme in order to discredit it? No one here mentioned being sealed in a "cabin of doom", as the blend is likely 80/20. The issue was the shortcoming of the OP's process of switching to recirculation with A/C off as an alternative to a cold cabin, instead of merely changing the temperature setting. MB itself, in the Owner Manual, indicates the short-term purpose of the recirculation function, and the underlying issue is the increase in humidity and deterioration of the air quality, not to lethal levels of course, but sub-optimal.
^^This is the statement I was referring to. You would have to be sealed off from fresh air for a LONG time in the context of a car interior for a person to pass out. Much longer than it'd take for the exhaust's carbon monoxide to knock you unconcious.
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From: Southwest USA
Another round of ICE
We agree again! The issue is not losing consciousness...no need to go to that extreme...it is comfort, optimal alertness, and glass clarity (recall the OP turns off the A/C when he uses recirculate).
Senior Member
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From: RI
2017 S550 4matic
If that's what you mean by 'we agree again' then I suppose that's true. Otherwise, I haven't the slightest idea what you mean.
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Joined: Jan 2009
Posts: 5,113
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From: Southwest USA
Another round of ICE
the point I was rebutting (which by the way wasn't even your own statement) stated that the recirc shuts off to prevent losing conciousness, which I stated was a complete and total farse.
If that's what you mean by 'we agree again' then I suppose that's true. Otherwise, I haven't the slightest idea what you mean.
If that's what you mean by 'we agree again' then I suppose that's true. Otherwise, I haven't the slightest idea what you mean.
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Joined: Apr 2006
Posts: 2,139
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Tesla Model S P100D
you guys honestly believe that mercedes engineers would allow the recirc option to seal you into a CO2 cabin of doom? Seriously?!
NO recirc system on any car ever completely seals off the outside air. SOME outside air ALWAYS gets in, regardless of the car. Why do luxury cars seem to be better? Because ALL the air going into the cabin goes through the cabin filter.
The recirc may be on a timer, that's one thing. But I (at 6'2" and 240lbs) certainly put out more Co2 than a 5'4" female that weighs 90lbs. So while the recirc shutoff (if it even works the way you say it does) may correct the air quality for her, what happens when my much higher Co2 output overruns that?
This discussion is in the weeds as far as what the OP posted...I'm shocked we're talking about oxygen contents in a conversation about an HVAC setting in our cars...
NO recirc system on any car ever completely seals off the outside air. SOME outside air ALWAYS gets in, regardless of the car. Why do luxury cars seem to be better? Because ALL the air going into the cabin goes through the cabin filter.
The recirc may be on a timer, that's one thing. But I (at 6'2" and 240lbs) certainly put out more Co2 than a 5'4" female that weighs 90lbs. So while the recirc shutoff (if it even works the way you say it does) may correct the air quality for her, what happens when my much higher Co2 output overruns that?
This discussion is in the weeds as far as what the OP posted...I'm shocked we're talking about oxygen contents in a conversation about an HVAC setting in our cars...
Senior Member
Joined: Aug 2011
Posts: 356
Likes: 19
From: RI
2017 S550 4matic
Why are you quoting me to disclaim something I never said? I never said someone is going to die in a cabin of doom. I just said that the CO2 levels will probably go up if you recirculate the same air. You might not die from it but it is probably not ideal as Sportstick has already tried to explain to you. I don't understand what you are arguing about honestly. We are all just trying to help the OP to use the automatic climate control system as it was intended to be used.
Bottom line, by the time the recirc causes you any issues it'll be the exhaust gases from sitting with the car running that will get you long before you breathe yourself out of oxygen. No need to spook the OP. Accurate information is important, especially if your outlandish claims were to push the OP to bring his car in for a diagnostic, which we all know is far from cheap.
Newbie
Joined: Jan 2013
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c300
Jcat ; dont back down, you are correct about MB forcing the air recirc off.
i was kinda surprised (well not really) on the number of loyalists that believe in that you need fresh air after just 5 minutes of being recirculated. they really believ after 5 minutes, there is a risk of getting diizzy, not as alert ?
i would not care if it was a 1 hour recirc shutoff (even though i dont believe in it), but 5 minutes - totally wrong.
i was kinda surprised (well not really) on the number of loyalists that believe in that you need fresh air after just 5 minutes of being recirculated. they really believ after 5 minutes, there is a risk of getting diizzy, not as alert ?
i would not care if it was a 1 hour recirc shutoff (even though i dont believe in it), but 5 minutes - totally wrong.
Newbie
Joined: Oct 2014
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2012 E350
Hi I am new to MB but I am battling a foul smell from the AC system which is very well documented here as mold issue arising from wet evaporator coil. While I was experimenting with this problem, I noticed that the damper does not respond to "Recirc" button during Manual mode. I understand that computer figures out how much the damper opens up when its' in AUTO mode, but why can't I not control this under manual mode? What is the purpose of having this Recirc button if I can't control it? If I can drive with damper open, I think I can help prevent the mold growth in the evaporator coil. BTW, I went to the dealer and they were no help.
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Joined: Apr 2019
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2004 S500
Actually I am a new user and appreciate what the user said about the holding of the recirculate button. I would not of known otherwise. Just because you dont think his information is relevant doesnt mean others feel the same. This site after all is for everyone.
