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Old 10-04-2001, 11:26 PM
pmizell's Avatar
Benz Zealot
Join Date: Jun 2001
Location: Houston, Texas
Posts: 838
Recirculated air?

First off, as I'm unaware of later MB chassis designs so I can't speak for them, I'd just like to say that the 124 design with default setting of outside air was bad engineering.

Not only that, but to have the system not "remember" your preference for recirculated air when you start up the car and having to hit the dash button every time you're behind a smoking car is a pain in the #%#$ too.

To top it off, the "recirculated" setting doesn't seem to truly keep out outside air, at least not in my 300E. It could be a problem with my particular car, but I can still smell traces of unwanted outside air with the little red button lit up.

Anyone else have this same problem, or feel as I do?

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Old 10-05-2001, 12:06 AM
JCE's Avatar
JCE JCE is offline
Down to the Wear Bars
Join Date: May 1999
Location: So Kalifornia
Posts: 2,189
Actually, the recirculated air was probably an effort to make sure no mold built up inside the AC system. My 88 Acura Legend had foul odors, and they kept insisting I was using the recirculation button as a default, and handed me a factory bulletin that said recirculate should not be used for more than 10 minutes as it allowed mold to grow, and that I should always shut off the AC and use only fresh outside air thru the system each time I was within 5 minutes from my destination!!! Their point was to never use the recirculate button except to cool down the hot car during the first 5 minutes of driving, then use AC/outside, and for the last 5 minutes, use non-AC outside. I kept explaining that was what I did, except for the last 5 minute procedure, but they wouldn't do anything about it!

There is also an unanticipated benefit to a default outside air position. About 10 years ago Atmospheric Chemists did an experiment on what setting was best in traffic jams: recirculated or outside air settings. On every car they tested, recirculated air tended to 'capture and concentrate' outside air pollution (seepage around windows and door frames, poorly closing vent doors, etc.) and always recirculation allowed worse levels inside the car than either 'fresh air' setttings, or than the outside air at window level!

My 98 C230 defaults to outside, and I believe is time limited to the duration on recirc, just like my 87. Hope this helps.

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Old 10-05-2001, 01:48 AM
Registered User
Join Date: Jun 1999
Location: Surrey, Beautiful British Columbia, Canada
Posts: 750
well said John. all honda cars i owned and still use do exactly
that, and so with my 89 300e.
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Old 10-05-2001, 08:23 AM
N. Gilbert
Posts: n/a
I too have noticed this while sitting in the Detroit traffic jams. If I select re-circulate, I expect it to stay in that position. After 10 min. it changes back to outside air. I thought it was yet another electrical quirk... It is distracting since by the time it changes back, my mind has focused on something else. I am reminded it has changed when I get a cloud of fumes in the car. Maybe I should be patient and the car will eventually have me trained...
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Old 10-05-2001, 08:05 PM
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Join Date: Jun 2001
Location: Omaha, NE
Posts: 962
The reason MB engineers set up the climate control system to default to outside air was simple: SAFETY. Remember, this is the company that engineers its hoods to be springy so that unwary pedestrians will bounce off; the company that heats up windshield washer fluid so it doesn't freeze when it hits your windshield; puts sensors on its brake pads to warn us when brake pad material is getting thin . . .

For those of us in cold winter country, recirculating cabin air in the winter is a good way to almost instantly fog up one's windows. I've done it with a Honda I once owned, and almost every day in the winter see drivers with completely fogged-up windows.

My owner's manual tells me that the boys and girls in Stuttgart set it up so that you get recirculated air for 30 minutes after hitting the switch if ambient temp is above 45 degrees F, and only 5 minutes if temp < 45.

I think it's a really ELEGANT solution to human forgetfulness.
'93 400E
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