Windows not de-misting

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NAG

New Member
Joined
May 22, 2005
Messages
16
Location
Scotland
Car
1998 c240 sport
Hello Folks

I recently became the proud owner of my first ever mercedes benz :D and consequently a new member of MBClub UK :)
So far am very happy with the car, its a beautiful car that drives really nicely and its the right colour.

However, there is a small problem.
The windows don't seem to de-mist properly.
Its especially bad when there are people in the car.
When the windows start to steam, I do as the manual says, AC off, temperature wheels set witht he white part (even tried increasing the temperature) in the middle and blowers set for air to come out at the windscreen and dash. Oh yes, and the centre vents I close.

The windscreen does demist a bit i.e bottom half is fine but top half just stays the same.
The front side windows start to demist slightly also, forget the back windows they just stay in a permanent state of misted-ness.

Air is definetly coming out of the vents nearest the windscreen and at the side at the correct temperature.
If I set the fan to the highest speed maybe de-mists a little bit more but nothing great.

Oh yes, one last thing to mention. Before I bought the car the dealer replaced the windscreen due to a bad stonechip/crack type situation.
I am assuming the correct one was fitted, it certainly looks fine.

Anyhow, thats all the information I can think of relating to the problem.

Anyone with information/similiar experiences would be most appreciated.
I am probably going to book in with mercedes-benz, the warranty I have is one of those that excludes wearable items, but I'd like to have some idea/understanding about the problem myself before going down this route.

Thanks and Kind Regards
 
Hi NAG

It sounds like the aircon is not working and is not drying the air.

The aircon can be turned off using a button marked EC which means "Economy". This allows the fans to blow but does not run the compressor. This button has a light. If the light is on then you are in EC mode - aircon is off, and demisting will be very poor. Make sure this light is off, so that aircon is running.

If the light is off and you still get poor demisting then I think you need to get the aircon checked over.
 
dont know how the A/C system works not having one :( but if the windows are not clearing its (obviously) the moist air in the car from breathing that is not escaping.

Try and ensure the recirculating button/switch is not in recirculating mode if you have one . . . because you need air from the outside to clear it
 
Welcome to the forum!

If you've got AC turn it on as AC dries the air, this will help with the demisting. AC units in Mercedes are highly effective - I'm sure you'll be mist free in minutes.

Best of luck!
 
Doh....So far I have been trying to de-mist without any AC on at all :eek:

Apologies folks for the daft question and thanks for the excellent response, I read the manual(s) but obviously not carefully enough !

So let me get this, in a situation like yesterdy (pouring rain outside and windows steaming up badly with two passengers) to de-mist the windows AC needs to be switched on and once they are de-misted I can switch back to EC mode, or do I need to keep the AC on permanently?

I will test out the AC and let you know how it goes :)
 
NAG said:
...
So let me get this, in a situation like yesterdy (pouring rain outside and windows steaming up badly with two passengers) to de-mist the windows AC needs to be switched on and once they are de-misted I can switch back to EC mode, or do I need to keep the AC on permanently?
...QUOTE]

AC will demist the windows very effectively. Most people just leave it on all the time.

If for some reason you prefer to turn it off, please note that you should really run it from time to time as the refrigerant is also a lubricant for the seals in the sytem.

Most people are of the opinion that the cost of running it is so small as to be incalculable. The only reason I can think of not to use it would be if you like to have your windows open, plus maybe contact lense wearers who drive long distances could suffer from dryness?

Even in the winter I find dry warm air much more comfortable than damp warm air, so I leave mine on all the time.
 
If you don't run A/C all the time you have to remember to run it for at least 20 minutes once a week to lubricate all the seals (as said above). Then, you have to run hot air through the system for another 20 minutes to ensure that all the condensed moisture in the ducting (caused by the warm air arriving in a nice, dry, chilled duct) is fully purged otherwise horrible bacteria will grow in the damp conditions and cause an awful smell that never really goes away.

Unless you are towing an over-sized caravan across Dartmoor and need the extra few BHP that Air con saps from the motor, I would strongly advise leaving it on at all times.

Believe me, you do not want that I-save-a-few-pee-per-week-by-leaving-the-aircon-off smell in your car, it is ugh! (Had it for 3 years in my BMW, the only cure is a For Sale advert in AutoTrader).
 
Hi NAG,

**Snap** Nice car :p

I agree with what the others have posted above.

Leave AC on (no EC light) for demisting, as this routes incoming air through a de-humidifier.

Leave AC on all the time as it is better for the system.

If you find you're still having problems then check the pollen filters, it's fitted under the dash, or get a garage/dealer to check them for you. Also a quick and easy test of your system is to turn the dials all the way to the blue and turn the fan speed up on a fairly warm day, the air should then blow really cold after a min or so, if the air only blows out slightly cool or warm then that's a good indicator that your AC system has lost gas.

Good luck getting it sorted :)

S.
 
Thanks guys.
I have now been running with the AC on permanently.
Never having had AC in any of my previous cars, I thought that AC is only necessary in extreme conditions but from the going by your responses, its more a necessity than an option.

Typically when I want to test it, the weather goes all sunny and dry :) so I'll have to wait for the next downpour.

One thing I have noticed is when I initially switch the AC on there is a slight hint of a pong for a short while (less than a minute) then its fine. I suspect this is the smell pprandall51 refers to (yes, it is nasty :( ). I've had the car a week + 1 day and have for most of that time been running with AC off.
I reckon probably need to do the 20 minutes cold then hot thing, or do you reckon the pong is now here to stay :eek:

Steve, the test you mention works fine, the air is freezing cold very quickly, so I reckon the gas is fine.

Excellent folks, I'll perhaps get the dealer to check the pollen/dust filter but other than that I think its a case of wait for the rain/temperature drop to confirm that all is well with de-misting the windows.
I'm worried though with it being summer now I won't get the chance, what with all the great weather we'll be having :rolleyes:
 
From memory you will get the pong back the moment that moist air gets the chance to get into the ducting - the moisture re-awakens the pongy bacteria and it smells. Moist air = a/c off....

I think that you will not be troubled by it if you keep a/c on all the time.

It is such a common problem that there are now special kits on the market you can use to sterilise the ducting. I think Halfords sell one. There are also specialist companies that can do a full sterilisation of the ducting.

I'd try Halfords first.

Good luck!

Philip
 
NAG said:
So let me get this, in a situation like yesterdy (pouring rain outside and windows steaming up badly with two passengers) to de-mist the windows AC needs to be switched on and once they are de-misted I can switch back to EC mode, or do I need to keep the AC on permanently?
If you do turn the A/C on and off manually (I do) then you'll find that in wet weather, once you've used the A/C to demist the car, if you then turn it off the car will mist up straight away as it drags in wet air off the condenser.
I try to remember to turn mine off a few mins from home, otherwise it steams up straight away when next used (unless A/C is switched on).
 

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