Any ideas and why on a cool morning, 10°c today. When I accelerate rapidly, the rear window of my Vrs estate mists over. Do you think its the warm air being pushed to the rear and making contact with the cold screen.

Are you running with AC on or off? If there is moisture in the air, on cold, damp or rainy days, the windows will mist up unless you keep the AC on which dehumidifies the air and clears the screens. If you switch the heater to fast clear the front screen, you should notice the AC fires up for this reason, so you can replicate this on low fan by just keeping the AC on all the time and the rear windows should stay clear as a result.

Ac always on.It only occurs when the foot goes down, clears when I ease off.As I say, I think it must be due to the sudden movement of air

Any ideas and why on a cool morning, 10°c today. When I accelerate rapidly, the rear window of my Vrs estate mists over. Do you think its the warm air being pushed to the rear and making contact with the cold screen.

My fluid dynamics is basic, at best, but it would be the cool air that is pushed to the back when you accelerate?

 

But, also, the faster you go the more cold air outside is passing over the window which would make the glass colder.

By foot goes down, you mean to the floor right  ?

 

This is probably because when you accelerate hard the AC system is temporarily disabled to give max power to the engine (same with electrical loads e.g. heated screens are disabled during hard acceleration).

When you back off or after a maximum time at high load, the systems are turned back on.

Edited 7 November, 201411 yr by Gabbo

Air comes in the car through the vents in the dash and exists though vents in the boot (like all cars) so the cooler air is always going to the back....

My experience is that the misting occurs on the outside of the window and is is a result of the exhaust vapours condensing on the cold back window.

My experience is that the misting occurs on the outside of the window and is is a result of the exhaust vapours condensing on the cold back window.

I was about to say the same. My vrs tsi estate evenly mists the rear window when I accelerate hard and its cool outside. Its always done it and if I run the rear wiper it clears it if I'm quick enough as it clears almost instantly on its own anyway.

My car mists up quite badly in damp cold weather even with the AC on, only thing that does seem to clear it ai sticking max demist on the front screen.

As far as I can tell the anti fogging sensor that the climatronic has seems to be doing jack! Sure its functional though as my stop start has once before been deactivated to prevent misting.

...that said I have not cleaned the interior glass since buying the car and has alot of new car clag over it; probably isnt helping matters to be fair

I keep a small dehumidifier (that you can plug in and dry out when its saturated) in the car and that helps keep the car from misting up, lasts about a month between charges

...that said I have not cleaned the interior glass since buying the car and has alot of new car clag over it; probably isnt helping matters to be fair

 

This makes a big difference on my front screen.

I wipe it once a month with a "magic window cloth" from one of the pound shops, seems to do a great job.