Another air con thread

robmc52

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W220 2005 S320 CDI Previously...W210 2002 220cdi, W202 2000 C200T Kompressor
Sorry! :p The system in my W210 works fine as far as I know but I've noticed that if it's a hot day, say 24, 25 degrees, and I start the engine, the recirculation flap will shut for a couple of minutes. Now it's really hot weather the system is still blowing cold air but the flap is shut all of the time.

I have noticed that on a warm day that adjusting one or other of the temperature control wheels a fraction, to slightly hotter, will cause the flap to open, but this past week or so trying this doesn't make any difference, the flap will stay closed.

If I try it during the evenings, when the temperature has dropped below 20 degrees or so, the flap won't close on start up. So, the question is, does it just need gassing up a bit, or, as is normally my luck, something considerably more expensive?

cheers
Rob
 

Lexman8

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I'm not sure there actually is a problem with your car, unless I've misunderstood.

Climate systems are normally designed so that having taken temperature readings inside and outside the car and compared those with the desired temperatue as set on the controls, it'll set the recirculation flap closed (i.e. ON) if there is a big differential so as to speed up the cooling of the interior. So on a very hot day, recirculation can stay on for quite a while. Selecting a higher temperature on the controls then reduces the temperature differential so the flap opens. Similarly, when it's cooler outside the differential is less so the flap won't close.

I can't check it on my Merc as the aircon isn't working but that certainly how it works on my Lexus and Honda.
 

cleverdicky

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Mine does something similar but it is affected by the position dial.
I know when its set to point at feet, the flap closes, but with it set to (left arrow??) all the vents blow ;)
 

Corned

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2005 S211 E320CDI Avantgarde
Sorry! :p The system in my W210 works fine as far as I know but I've noticed that if it's a hot day, say 24, 25 degrees, and I start the engine, the recirculation flap will shut for a couple of minutes. Now it's really hot weather the system is still blowing cold air but the flap is shut all of the time.

I have noticed that on a warm day that adjusting one or other of the temperature control wheels a fraction, to slightly hotter, will cause the flap to open, but this past week or so trying this doesn't make any difference, the flap will stay closed.

If I try it during the evenings, when the temperature has dropped below 20 degrees or so, the flap won't close on start up. So, the question is, does it just need gassing up a bit, or, as is normally my luck, something considerably more expensive?

cheers
Rob

Sounds to me like normal (and desirable) operation. With a large temp differential (current inside temp versus selected temp) the system will do what it can to make up the difference as fast as possible. With higher ambient temps, there is no point cooling hot outside air and pumping it into the cabin. Much better to re-cool already cooled air already inside the cabin.

Then when the temp differential is low enough to be managed, fresh air can be re-introduced again.

Sounds like it's working perfectly normally to me.
 
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robmc52

robmc52

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W220 2005 S320 CDI Previously...W210 2002 220cdi, W202 2000 C200T Kompressor
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Well, thanks for the replies, I can follow the logic of it now. It's only been in the last few moths that I've noticed it happening after owning the car for five years, does this mean global warming is real?!
 

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