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Model specific boards => Golf mk7 => Topic started by: andyb_123 on 18 March 2018, 17:58
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We occasionally press the recirculate utton (when going through a tunnel or following a car with a cloud of blue smoke behind it).
We notice doing so causes the interior to start fogging up, which is really annoying. It's happened a few times.
Our old MK5 never had this problem. Is this common in Mk7s?
The aircon is usually left on 'auto'. Sometimes I'm driving in "normal", sometimes in "eco".
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that happened for me on my mk5 and my mk7. if its on eco, it won't be performing fully, so I would leave it on normal.
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If you are in "eco" the aircon is set to super low and probably can't even clear the windows.
Why are you using eco? It absolutely saves bugger all fuel. Don't be fooled by it!
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I use eco if doing a boring slowish motorway journey. It's the only mode where "freewheeling" happens, which does seem to use less petrol than when in normal - on some stretches, the car's basically idling for a mile or so. If I need a quick burst, I stick the DSG into sport mode for a bit.
I usually have it in sport mode for country lanes or whatever.
The fogging up happened with the car in "normal" mode, so the aircon wasn't in low power mode, though it was about -2 outside. The first time it happened (going through the Rotherhithe Tunnel) it was a bit scary as the lanes are ridiculously narrow and stabbing at the controls took my eye off the road.
The MK5 never did this to us. It would use the aircon to remove all the moisture when recirc was on, which is what I'd expect with the MK7 too. It's the only thing about the car which is a regression from the MK5.
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Recirculate doesn't let any fresh air into the car. This is needed to draw air through the car, taking moisture with it. At this time of year the car will have more moisture in it due to wet shoes and coats, so not allowing fresh air in will cause the condensation.
Cars, like new houses, are so well sealed these days that air doesn't move around freely. In the old days the draft under your front door would help the chimney draw and the fire burn well. Nowadays we need trickle vents or mechanical fans to make the fireplace work.
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Recirculate doesn't let any fresh air into the car. This is needed to draw air through the car, taking moisture with it. At this time of year the car will have more moisture in it due to wet shoes and coats, so not allowing fresh air in will cause the condensation.
^This.
OP; I can understand you might want to use recirculating mode when going through tunnel to stop other cars exhaust fumes entering your car. However, if it was a choice between fumes for a few minutes and being able to see or no fumes and your vision being blocked by condensation, I’d always go for the former..
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In the Mk5, when you put recirculate on, it turns the aircon on.
The aircon system extracts moisture from the air, preventing steaming up when recirc is on. If there was no aircon, then sure, recirc would allow the moisture to build up. You see some cars steamed up like this because the owner has no idea about their air controls.
The manual explains this. We sometimes had the recirc on for 30 minutes or more (forgot to switch it off) - never had fogging issues in the Mk5.
Perhaps it'll stop being an issue when things warm up a bit, but still... An integrated aircon system shouldn't let the car steam up...
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Used correctly the mk7 system doesn't steam up.
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"Used correctly the mk7 system doesn't steam up."
What am I doing wrong then?
-Air con in "auto"
-Normal mode
-Press Recirc
-Car steams up.
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Get in car and press the auto button, that's it. Don't touch it ever again :grin: seriously though in this weather at the moment your more likely to have moisture in the car so pressing recirculation button will steam the windows up. Have you had the system checked for faults? Filters changed? I haven't pressed the recirculate button on any car I've had ever. All your doing really is moving the existing air in the car which to be honest why would you do it.
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The only time I use recirculate (apart from when it does it automatically when reversing) is when the temperature is really hot in summer. It is more efficient to recirculate already cooled air, rather than drawing in warm air from outside only to have to cool that.
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I never use recirculating mode in my car either; have the a/c on ‘Auto’ and leave it and forget about it.
Have you checked your car’s carpets to make sure they’re not damp?, which might indicate a faulty door/window seal. Damp coats/umbrellas inside a warm car at this time of year with the air con in recirculating mode would be creating the ideal conditions for the interior windows to mist up.
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"All your doing really is moving the existing air in the car which to be honest why would you do it."
I would do it when driving through a tunnel, where the air quickly becomes thick with diesel and fumes, or when following a car which is spewing out blue smoke.
It's also good when it's really hot to reduce the temperature more quickly.
These are all reasons why there is a recirculate feature in the car.
To repeat, this feature is on the Mk5 gti too. It never steamed up once when on auto and recirc was on in 10 years, and we use it a lot.
It's a brand new car - done 3k miles. I'll mention it during the first service.
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How long is it recirculating for before it starts to fog up? My Mk5 would fog up eventually if it was in recirculation mode on longer journeys. I don't find the Mk7.5 much different really.
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Aircon on recirculate should normally stip the moisture out of the air, but below *I think* 5 DegC the aircon compressor is deactivated to protect itself. This has always been the case on all cars. This is why it won't condense moisture out of the air when its cold outside.
Also, as said recirc is literally cycling the damp air round the car - moisture that can come from wet clothes, mats and also from your breath - you expel a lot of moisture all the time.
Its not surprising at all what you experienced to be honest.