Windscreen Demisting

Technical Forum for the Porsche Macan
Paul1970
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Post by Paul1970 »

Apologies if this has been answered somewhere but I have looked and can’t find.

Anyway, tonight was wet, warm and humid. There was condensation on the lower part of the windscreen.

The first thing I tried was the auto windscreen button but ridiculously that only seems to blast hot air at high speed. Given it was 20 degrees this dis not go down well with the passengers (or me) so I switched to “max a/c” This blasted out AC but had no effect at all (I was expecting to see it evaporate quickly)

Any advice gratefully received about effective internal demisting.

Thanks.






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Nuclear Nick
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Post by Nuclear Nick »

If you leave the ventilation system permanently on 'Auto', set on either 21 or 22 degrees, it will look after itself and you won't get screen misting. There is no need to to anything else apart from opening all the windows/pano roof for a short time to release hot air after the car has been parked in the sun. Resist the temptation to fiddle with the settings!

It's also important to keep the inside of the screen squeaky clean. This helps stop moisture gathering in the first place and speeds its removal if it does appear in extreme conditions, usually cold winter nights and mornings. This stuff is one of the best products I've used - https://diamondbriteshop.co.uk/catalog/ ... tegory/34/
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nsm3
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Post by nsm3 »

If external conditions are warm and humid, it means that the external air is fairly well saturated and in its current condition, can't absorb much more in the way of water. This is the reverse of the winter situation, where the air may be saturated, but by simple heating, it's moisture carrying capacity can be increased dramatically. It's quite possible that in the warm/humid conditions, putting the a/c on max and setting the system to recirculating mode, will speed up the demisting process, as the car will remove moisture and pump drier and drier air into the cabin, which in turn should 'suck' the moisture off the screen.
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Col Lamb
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Post by Col Lamb »

Sometimes the whole screen can mist up, irrespective of the AC system being set to Auto or Manual.

Misting in a Macan just happens but only in specific weather conditions, it is a well known occurance, its annoying but the whole Macan AC system is very poor anyway.

It should not happen as the AC system should sense the temperature and humidity of the incoming air and if needed it should operate the chiller coil when the saturated air deposits much of the moisture which then drips down under the car rather than depositing itself on the coldest surface inside the car which is the screen. This method of control does not seem to take place within a Macan.
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Giz9
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Post by Giz9 »

Make sure that the Auto-Recirculation setting is switched On. That makes a big difference. When I first got my Macan, I switched this setting off because I thought I wanted the maximum amount of fresh air. However, I got misting up problems. When I switched Auto-Recirculation back on, these went away and have never been a problem since.

My conclusion is that, if the outside air is near satuaration, the A/C cannot dry it quickly enough. Auto-recirculation gives it a bit longer to work on it.
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Paul
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Post by Paul »

Nick & Giz do exactly what I do (now)
When I first got my 2015 SD I would manually direct the air flow to the screen as I have always done with previous cars. Misty screen soon followed and, as you say, the max demist button simply blasts hot air at onto the screen.
A quick read of the manual (😳) and setting to full auto and sync at 19-22 always worked a treat.
Same with my current GTS.
The only time it fails is if Mrs P has started to fiddle with “ her side.” If she changes her temp and / or directional flow, the auto light goes out and a misty screen may soon follow depending on the circumstance outside.
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happy days
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Post by happy days »

When I first read this, I thought it might be misting on the outside of the screen where the cold air blows, but having re-read I'm clearly wrong.
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Paul1970
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Post by Paul1970 »

Thanks for the advice. I shall try the “Auto” route but I know it will be very hard to keep my hands off fiddling with it, especially when the wife and kids moan about cold air blasting out!


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Alfanut
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Post by Alfanut »

After a month with the face lifted Macan, the screen demisting is driving me nuts. It ain’t right.
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Makanik
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Post by Makanik »

Alfanut wrote: Thu Jul 18, 2019 12:24 am After a month with the face lifted Macan, the screen demisting is driving me nuts. It ain’t right.
What exactly is the problem?

Do you ensure that the Auto, A/C and Synch lights are all always on?
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