CLS constantly misting up - what to check?
Discussion
I've a 2017 CLS shooting brake, still in warranty but before I go through the hassle of booking the car into Merc I wondered if anyone else had suffered similar or had any ideas of common issues or simple things to check.
Firstly, the fan seems very weak even on full and directed to windscreen - makes a lot of noise but not much comes out and it seems to only come through the centre section. Can anyone with a CLS confirm if the fan is just noisy and weak?
Carpets seem dry, no signs of water internally after power washing car, a/c being on doesn't seem to make a difference, no wet umbrellas anywhere, interior glass has been cleaned with autoglym fastglass and mr muscle - I've tried everything I can think of.
One weird thing it does is that the windscreen can often be clear when I get into the car, but when I start the engine and the fan starts, the windscreen them mists up - not sure if water could get into the hvac system or if there's a simple way for me to check?
TIA!
Firstly, the fan seems very weak even on full and directed to windscreen - makes a lot of noise but not much comes out and it seems to only come through the centre section. Can anyone with a CLS confirm if the fan is just noisy and weak?
Carpets seem dry, no signs of water internally after power washing car, a/c being on doesn't seem to make a difference, no wet umbrellas anywhere, interior glass has been cleaned with autoglym fastglass and mr muscle - I've tried everything I can think of.
One weird thing it does is that the windscreen can often be clear when I get into the car, but when I start the engine and the fan starts, the windscreen them mists up - not sure if water could get into the hvac system or if there's a simple way for me to check?
TIA!
Had this with my car, new in 2017, but Not A Merc. In winter the car was so misted up even with heater on full and recirc off , I had to run the air-con.
Someone else on PH suggested dessicant dryers like these. Small plastic pot, with absorbent white pellets. Put pot in the back of the car, and ten days later the problem is gone.
So presume cold damp air gets into car, condensation forms inside and soaks into seats and carpets. Amateur diagnosis confirmed one cold night when opened boot and found v.damp carpets, running condensation on metalwork, but no leak.
Problem resolved. The white pellets in these things spill out in a car, so plastic box is in a carrier bag and wedged under the passenger seat. No more mist.
Loads of other types around. Damp Kontrol:
https://www.amazon.co.uk/Kontrol-Streamline-Moistu...
Someone else on PH suggested dessicant dryers like these. Small plastic pot, with absorbent white pellets. Put pot in the back of the car, and ten days later the problem is gone.
So presume cold damp air gets into car, condensation forms inside and soaks into seats and carpets. Amateur diagnosis confirmed one cold night when opened boot and found v.damp carpets, running condensation on metalwork, but no leak.
Problem resolved. The white pellets in these things spill out in a car, so plastic box is in a carrier bag and wedged under the passenger seat. No more mist.
Loads of other types around. Damp Kontrol:
https://www.amazon.co.uk/Kontrol-Streamline-Moistu...
Our CLS saloon (can't bring myself to describe it as a coupe) is the most mist-up-prone vehicle we have. Not just windscreen but also side and rear windows.
On full blast fan is a little noisy and it does struggle to really chuck out furnace levels of heat. It is the only diesel out of nine cars and I've often wondered if there's something around that which makes it more prone to misting up. Certainly on a cold morning you have to warm the car up well before venturing out.
On full blast fan is a little noisy and it does struggle to really chuck out furnace levels of heat. It is the only diesel out of nine cars and I've often wondered if there's something around that which makes it more prone to misting up. Certainly on a cold morning you have to warm the car up well before venturing out.
AREA said:
Our CLS saloon (can't bring myself to describe it as a coupe) is the most mist-up-prone vehicle we have. Not just windscreen but also side and rear windows.
On full blast fan is a little noisy and it does struggle to really chuck out furnace levels of heat. It is the only diesel out of nine cars and I've often wondered if there's something around that which makes it more prone to misting up. Certainly on a cold morning you have to warm the car up well before venturing out.
Oh go on, Ive referred to mine as a 'shooting brake' so just call it a coupe and Ill feel less of an idiot.On full blast fan is a little noisy and it does struggle to really chuck out furnace levels of heat. It is the only diesel out of nine cars and I've often wondered if there's something around that which makes it more prone to misting up. Certainly on a cold morning you have to warm the car up well before venturing out.
Interesting, I wonder if the raked front and rear screens make the screens more likely to have moisture condense on them.
Re: the above recommendation, thanks, I do already use a dehumidifier- little bag that you dry out now and then in the microwave then pop back in - helps slightly.
I just checked the dessicant box in the car. 1/2 litre of condensate in it after a month.
Edit: these contain Calcium Chloride, it turns to a milky mush. So if the container spills, you got milky salty mush in your carpets.
So will try those silica gel packs.
Edit: these contain Calcium Chloride, it turns to a milky mush. So if the container spills, you got milky salty mush in your carpets.
So will try those silica gel packs.
Edited by Slushbox on Thursday 17th January 14:07
I have a 2011 CLS petrol. It is also bad at demisting, always has been. Takes a few minutes to clear the windscreen sometimes when other cars would zap it quickly (wife's Fiesta with a heated windscreen is best, clears anything quickly). In theory the gubbins are the same as an E-Class so does anyone have issues with one of those?
Not on either of our current two E's, or the last one (or the C's before them) just tap the max defrost button in the morning and it clears quickly, didn't really have the problem on the 17 plate CLS I had for a while, even through Feb / March
Apart from the first reply I made on the thread have you had a look in the spare wheel well (if it has one), I've found pools of water in those in various cars over the years
Apart from the first reply I made on the thread have you had a look in the spare wheel well (if it has one), I've found pools of water in those in various cars over the years
Edited by mk1coopers on Thursday 17th January 14:44
Targarama said:
In theory the gubbins are the same as an E-Class so does anyone have issues with one of those?
Which is one of the things puzzling me as the previous car was an E Class (same engine) and I had no such issues.I dont have an OBD reader so might just throw it at the dealer if all else fails, not sure what they'll charge me if they find nothing which is why I wanted to check the simple stuff first. And because I trust me, they are hit and miss.
It doesn't sound right, does it. My initial thought was that it's on 'recirc' but that's been ruled out.
Is it possible for you to check the aircon drain and the scuttle drains?
Blocked /poorly fitted pollen filter? As it's 2017 it's unlikely to have been changed unless it's high miles.
Is it possible for you to check the aircon drain and the scuttle drains?
Blocked /poorly fitted pollen filter? As it's 2017 it's unlikely to have been changed unless it's high miles.
I checked a few things over the weekend:
- carpets all dry, headlining dry around sunroof and door/boot apertures.
- boot underfloor is dry (no spare wheel well on this car, sacrificed for stupid blue-juice tank).
- poured a jug of hot water through the scuttle intake and it drains freely.
- the air intake system on this car is a removable black plastic box that sits above the battery, linking the scuttle air intake to the impeller behind the dash, hard to describe but it allows water through the scuttle to pass down through the drain, and air to pass horizontally through the internals of the box (which are empty, no filter or anything, and I'm not sure if there's supposed to be one in there) and to the impeller drawing it into the car.
- no idea where the a/c drain is to check it.
- can't find the pollen/cabin filter either, have had a poke around both footwells and there's a panel in the passenger side where your feet would rest that flips forward, only cables behind it - it's dry though - but no sign of any cabin filter.
- no vaping, smoking, or self inflicted fog ;-)
When I put the fan to windscreen only and increase to maximum the airflow does increase so the 'flap' is opening, perhaps not fully as the increase in noise isn't proportionate to the increase in airflow.
I've aired the car and put a bag of those dehumidifying crystals in it. If it persists it'll have to go to the dealer - I'm not tolerant enough to live with it!
- carpets all dry, headlining dry around sunroof and door/boot apertures.
- boot underfloor is dry (no spare wheel well on this car, sacrificed for stupid blue-juice tank).
- poured a jug of hot water through the scuttle intake and it drains freely.
- the air intake system on this car is a removable black plastic box that sits above the battery, linking the scuttle air intake to the impeller behind the dash, hard to describe but it allows water through the scuttle to pass down through the drain, and air to pass horizontally through the internals of the box (which are empty, no filter or anything, and I'm not sure if there's supposed to be one in there) and to the impeller drawing it into the car.
- no idea where the a/c drain is to check it.
- can't find the pollen/cabin filter either, have had a poke around both footwells and there's a panel in the passenger side where your feet would rest that flips forward, only cables behind it - it's dry though - but no sign of any cabin filter.
- no vaping, smoking, or self inflicted fog ;-)
When I put the fan to windscreen only and increase to maximum the airflow does increase so the 'flap' is opening, perhaps not fully as the increase in noise isn't proportionate to the increase in airflow.
I've aired the car and put a bag of those dehumidifying crystals in it. If it persists it'll have to go to the dealer - I'm not tolerant enough to live with it!
I've got a CLS Shooting Brake too and no such issues with condensation.
I have got the smelly aircon issue though which is pretty annoying. Something to do with mildew condensing inside the aircon system. You can flush the system but it comes back. Only fix is to run it hot or turn it off a few minutes from home.
I have got the smelly aircon issue though which is pretty annoying. Something to do with mildew condensing inside the aircon system. You can flush the system but it comes back. Only fix is to run it hot or turn it off a few minutes from home.
Check the AC is actually working - had something similar on my S6 and turns out the AC needed regassing due to a faulty fitting.
Symptoms were exactly the same as what you are having - easy to check by turning temp to minimum with AC off (in the S6 it's "economy"). Give it a few minutes and hold your hand in front of the vent. Keep your hand there and then turn the AC on and it should quickly get noticeably colder.
Symptoms were exactly the same as what you are having - easy to check by turning temp to minimum with AC off (in the S6 it's "economy"). Give it a few minutes and hold your hand in front of the vent. Keep your hand there and then turn the AC on and it should quickly get noticeably colder.
There's no condensation in my 2014 shooting brake, if the car is getting regularly warmed up the airmatic has a built in dehumidifier so it will keep inside the cabin dry. I have noticed the low air speed mentioned above when using the demist function but only following a cold start, I think it is preventing the driver from losing visibility as the windscreen can mist up quickly due to blowing damp air on it, also turning the temp setting up higher (24+) slows the air from vents.
I'd be tempted to take it to MB as it's in warranty, perhaps they can look at it under the Winter check...
For bad odours and general good health, a can of bilt hambers air con bomb works well. It can be discharged in the cabin with the air con in re-circ mode or directly into the system under the bonnet (keep hands and can clear of the cabin fan).
I'd be tempted to take it to MB as it's in warranty, perhaps they can look at it under the Winter check...
For bad odours and general good health, a can of bilt hambers air con bomb works well. It can be discharged in the cabin with the air con in re-circ mode or directly into the system under the bonnet (keep hands and can clear of the cabin fan).
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