Demisting the windscreen

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ScottBacon

Active Member
Joined
Oct 11, 2013
Messages
667
Car
F80 M3 Yas Marina Blue
Do any of you guys have problems getting the windscreen on the inside cleared in on a frosty morning. Mine is absolutely s***e ! I have to wait about 10 minutes for the thing to clear. I use the button on the centre console for 'quick' clearing the front screen - am I doing something wrong ?? :dk:
 
Possibly, You have water getting into the car somewhere.
 
You do have the a/c on?
 
You do have the a/c on?

I know a/c dries the air, but can't really see why it needs to be on, I don't bother and cars used to demist without it.
You would think a 6.2 litre petrol engine would generate quite a bit of waste heat very quickly.
 
The 55k pushes out warm air very quickly but defo needs the a/c on to demist effectively. My old SEAT was the same, turn off the a/c and demisting took ages.
The 203 IIRC actually disables the a/c at temps below 5c so demisting performance was terrible!
 
All my cars do and have always demisted fine without A/c. Perhaps the pollen filter is wet or blocked.
 
My 61 plate CLS 350 CDi is rubbish too, and always has been.

RR
 
The 55k pushes out warm air very quickly but defo needs the a/c on to demist effectively. My old SEAT was the same, turn off the a/c and demisting took ages.
The 203 IIRC actually disables the a/c at temps below 5c so demisting performance was terrible!
My CLS is exactly the same, rapid with A/C on.

Jules
 
My S210 is not too bad.

The X5 is rubbish. Got caught out nastily this week after leaving slightly before I should. I could see through just fine, but there was still a faint covering. Pulled onto the main road in a small gap to find the low sun completely blinding me. Had to turn off sharpish, and wait a few more minutes. I'll be more careful in future.
 
My other half complains of the same in our 2011 C63 estate, must use a gallon of fuel every morning demisting the screen.
 
I know a/c dries the air, but can't really see why it needs to be on, I don't bother and cars used to demist without it.

If the a/c has been on the day before then the evaporator will be wet. Start the car in the morning with the a/c off, or when it's too cold for the a/c to work, and the incoming air will pick up that water and dump it onto the screen.
 
My vw or rover manual, dont rem exactly which one, said that one reason for condensation is if you get in the car with wet clothes! Simple but overlooked. All the water will evaporate in the cabin!
:doh: or imagine your parked outside, frost, snow, below the car, start up car ... Move slowly...evaporation again... The humid air possibly is sucked in the car.

A bad senario... Your car exhaust produces a lot of H2O that gets sucked for some reason inside.

Or maybee humidity is simply accumulated due to recirc button on all the time... Use blower at higher speed helps.
Shut off ac, shut off hvac system completely, then turn it on leaving ac off, if you turn ac on compressor may run even if ac is off see tecn bulletin DTB P-B-94.20/05c JUN0 dont know if applicable f ur car though.
 
Sorry i think got the dtb number wrong. See attached for turning off ac compressor completely. Also to dry the evaporator you need to ( after you turn off the compressor as said) run the blower for at least half an hour with heating. So if the car has no other mulfunction, to avoid humidity, clean the window very well, ensure you dont import humidity yourself in the car, and try not to turn on and off the ac as you get this vicious circle of temporarily storing humidity in the evap which is released when u turn off the ac.

By the way the odour treatment (wynns) is done after a contra cep Mb treatment so it wont work alone. Could not upload the whole doc but can paste the pages as photos if somenoe interested to read. There is also a recall for oil/acid smell/vinegar smell in car which is caused by the soundproofing material in the inside transmission tunnel in the car..not the ac directly. Has to be replaced.
 

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I have to admit, my W204 C220, with only 5000 miles on the clock is not nearly as good at demisting the screen as my previous Saab and Rover were, (both also diesels) and even more annoyingly clears the passenger side more quickly than the driver's.

On a different subject, call me old fashioned, out of touch or whatever, but may I make a request that while acronyms and recognised abbreviations are fine, the use of "txt spk" is avoided on the forum, please?

Thanks
Malcolm

(I can see the next post will be along the lines of "yep m8 ur old fshnd n out of tch.....):D
 
and even more annoyingly clears the passenger side more quickly than the driver's.:D

I've found spotless clean windscreens clear quicker than slightly dirty ones. Maybe the drivers side was cleaner?

Russ
 
I have to admit, my W204 C220, with only 5000 miles on the clock is not nearly as good at demisting the screen as my previous Saab and Rover were, (both also diesels) and even more annoyingly clears the passenger side more quickly than the driver's.

Mines the same 220 cdi 62 reg not as good as my old BMW, the Mercedes mists up when the BMW didn't. I put the aircon on to clear the problem, which takes the car out of eco mode. :dk:
 
If the a/c has been on the day before then the evaporator will be wet. Start the car in the morning with the a/c off, or when it's too cold for the a/c to work, and the incoming air will pick up that water and dump it onto the screen.

Good point. That is something I used to notice in my Peugeot 406.
 
My current car mists up, whereas the two previous E320 CDI's didnae.
 
Turn the A/c off and see what it does then. If still a problem, sacrifice the pollen filter as they hold moisture and significantly reduce airflow.
 
Thanks for the comments gents.

I usually have aircon on all the time, the car is 2013 so the aircon should be operating well. The bad news is that I have tried it without aircon on aswell. Still no better. Maybe a trip to the dealers because it takes approx 10 minutes to sort out. And yes, it is better on the passenger side too, as someone has mentioned.

It really is crap compared to my M3 which cleared in a matter of a 20-30 seconds :dk:
 

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