Windscreen Auto Demist

[peachjn]

My W210 has an automatic windscreen demister. It has no button to activate it but it senses (how ?) when it needs to override the aircon settings and turbo-blast hot air onto the windscreen. This used to work amazingly fine - at start-up in the summer it would come on for half-a-second, and in the winter for up to 5 minutes until the screen was pretty clear. Now however it comes on and stays on for upto 15 mins - by which time the car is like an oven.

I can't find any reference to this feature in the manual, does anyone know how to override the function, or perhaps where the sensor is that is triggering the auto demist. Its bad enough now in the winter but it will be intolerable in the summer.

 

[television]

Hello and welcome,need to get my head around this and will do so in the morning

 

[jberks]

I have to say I've never heard of this 'feature' either. My 210 certainly didn't do it and my 211, which has some very clever toys doesn't. Even my Dad's 211 with the all singing and dancing 4 zone digital climate system with sunlight sensors and all sorts doesn't do this.... so I suspect you are mistaking some other feature or possibly even a regulator fault for an auto demister.

 

[rf065]

One of my previous cars used to do this, no matter what the climate control was set to, in certain conditions when first started, it would direct all the air to the windscreen for a few minutes before returning to the original settings. Worked really well.

Russ

 

[jberks]

When I start mine up, assuming the interior is colder than the available heat, (Either after a restart or else 2 mins into a journey when the engine has warmed a bit) it does run the fan a lot faster until the interior starts to warm up and it may also direct more air towards the screen whilst it's doing this, possibly to avoid fogging, I'm not sure. However, thats just the heater trying to warm up the interior - not a sensor based screen clearer - which I'm pretty confident, doesn't exist ( and hence isn't detailed in your owners manual)

 

[jberks]

made a note of it this morning. 2-3 mins of half demist as it warmed up. Doesn't always do this so probably something to do with interior and engine temp differences, but all it's doing to warming up the interior. I guess it's just logical to direct most flow to the windscreen whilst it's doing it.

 

[whitenemesis]

Both options 580 and 581 have relative humidity sensors and depending on values and outside temp the system will direct air to the screen to help prevent misting.

The system also knows, via the restraint monitoring module what seats are occupied and if it is raining, via the RLS and will adopt dehumidifying setting to help prevent damp clothing from misting the windows!

The control units take inputs from the door modules, detecting open windows, from the ocp detecting open sun roof, from the cluster, monitoring ground speed and from the sun sensor (if fitted) or the light sensor, the intensity of the sunlight. and of course the outside temp.

Damn clever

 

[eGuru]

Both options 580 and 581 have relative humidity sensors and depending on values and outside temp the system will direct air to the screen to help prevent misting.

The system also knows, via the restraint monitoring module what seats are occupied and if it is raining, via the RLS and will adopt dehumidifying setting to help prevent damp clothing from misting the windows!

The control units take inputs from the door modules, detecting open windows, from the ocp detecting open sun roof, from the cluster, monitoring ground speed and from the sun sensor (if fitted) or the light sensor, the intensity of the sunlight. and of course the outside temp.

Damn clever

Now that is clever! Sadly I don't have either of those options:sad:

 

[JEZ.S320L]

Both options 580 and 581 have relative humidity sensors and depending on values and outside temp the system will direct air to the screen to help prevent misting.

The system also knows, via the restraint monitoring module what seats are occupied and if it is raining, via the RLS and will adopt dehumidifying setting to help prevent damp clothing from misting the windows!

The control units take inputs from the door modules, detecting open windows, from the ocp detecting open sun roof, from the cluster, monitoring ground speed and from the sun sensor (if fitted) or the light sensor, the intensity of the sunlight. and of course the outside temp.

Damn clever

Are you having a laugh? Yes? No? There's me thinking that 'Hill-Hold' was pretty clever

 

[television]

Are you having a laugh? Yes? No? There's me thinking that 'Hill-Hold' was pretty clever

The hill hold is only a Sprag clutch invented in 1800 and something, that comes into operation in W

 

[peachjn]

Thanks for the info and ideas

I don't have options 580 or 581, and the prolonged demist happens sporadically and seemingly unrelatedly to either the outside temperature or whether its raining or not, so I guess that means its an intermittently faulty regulator. Is there only one, and is it expensive ?

 

[Seeker_UK]

Damn clever

I could never have a car that's smarter than me...................