Rear Windows Steaming Up!

[xrm88]

Evening guys,

I’ve noticed our W212 has started misting up big time on the rear window while parked, and creeps forward to the side windows. It doesn’t take long to clear once the cars started but it’s bugging me and there’s clearly a problem. I’ve checked the seals around the doors and boot and checked the all carpets... everything seems ok?!
Can anyone help/advise?

Many thanks

 

[Jockcl500]

At this time of year it could just be cold damp air that is not dried, do you do short distance, run aircon/climate all the time?

 

[saff]

^^ I leave my aircon on all year round and never have problems with misting.

 

[xrm88]

Yeh fairly short - 30min commute max.
Only started using the heating since getting colder.

 

[zipdip]

I used to get that years ago,it came from to much activity on the back seat

 

[zipdip]

On a serious note,have you made certain that you do not have recirculate picked on the car,this will allow the car to warm up quicker but keeps the damp air in the car,you need fresh air in damp oair out

 

[whitenemesis]

But with a/c on and recirc on the air will dehumidify.
The fact it keeps coming back suggests a continuing source of water. Have you checked the spare wheel well and various cubbies under the boot floor?

 

[Jockcl500]

Every car I have had, I always run climate all the time on auto and never have a problem.
The recirculate is only really used if you are driving in a very smelly area, and will keep stale air in the car.
Run it on auto, recirculate off and make sure all the vents are open, if the air con is working properly it should not mist if you commute 30mins.
If you have had the aircon/climate off for any length of time, it will take a while to dry the interior properly, or may even need serviced.

 

[DSM10000]

Yeh fairly short - 30min commute max.
Only started using the heating since getting colder.

Heating is not the problem, is the air conditioning switched on?

 

[noogieman]

Are you fooling around with your lady in the backseat?
Windows do steam up very quickly!

 

[Rodd]

I have no idea if this is related, but I had the same problem in my Vauxhall Insignia a couple of years back. Turned out to be a leaking heater matrix which caused the carpet in the footwells to be constantly damp. I'm new to Mercedes, though, so this might be totally irrelevant as I'm sure they're designed quite differently to Vauxhalls! But just wanted to put it out there

 

[moonloops]

Change the cabin filter if it hasn't been done in a while.

There is also the classic of clearing all the exterior windows of water/mist with a cloth and then leaving the cloth in the car.

 

[Major774]

Two possibilities I can think of.

1. Reluctant to use A/C all year round
2. Leak in the cabin, or a damp item left in the cabin

 

[DSM10000]

A response from the OP would be helpful......

 

[johnsco]

If this is only a recent occurrence, it sounds like a source of water in the car.
Either a leak from outside, possibly into the boot area, or a leak from the heater.
With the aircon on and set to recirculate, this should dehumidify the air in the car.
But - Find the leak !

 

[SlimJim]

It’s simply warm air in the car condensing on the cold windows as the temperature drops over night.