Driving to work this morning, I had the air temperature set to "Lo" and the Window directional button selected. It was chucking it down outside, and the windscreen kept fogging up. To counteract this, I'd select the "Max" front windscreen button with enables aircon and clears the window in seconds. I didn't want it on the whole journey, so after de-selecting it, within minutes, the windscreen would fog up again. 

 

Any suggestions as to how I can prevent windscreen fog with a maximum blast of aircon?

Leave the AC on all the time, thats what it's there for.  Oh and keep in the inside of your windscreen clean.

Press the heated screen button  .

 

 

Sorry couldn't resist 

 

Seriously now, crack the rear windows open just a couple of mm, that allows the moisture somewhere to escape through.

Basically, the capacity of air to hold water vapour is closely related to its temperature - the warmer it is the more it will hold. So add a bit of heat and avoid chilling the air and glass.

 

The A/C also removes water by cooling it and taking water out on the condenser (which creates the pools of water on the drive that people worry about), and then heating it to the temperature specified by the A/C controls and sensors.

 

If the A/C is set to LO it chills the (probably already saturated) air as far as poss, and produces chilled saturated air - hence the fogging. 

You'll find if you run the climate without AC on in certain conditions the remaining condensate in the condenser will find its way back in to the cabin and cause the fogging.

Its probably best just to have the AC on all the time, the compressor is switched on and off intelligently as required in any case so its not particularly wasteful of fuel or engine power.

Also do be aware that when new the cabin materials emit an awful lot of clag....this gets transferred onto the glass and makes fogging worse. Give the front screen a damn good clean with a good automotive glass cleaner and damp cloth...wipe clean and dry with some paper towelling and all will be well.

I dread to think what the "clag" does to ones lungs! I had to clean the screen on my 7 month old Golf at the weekend care of the same thing and what was coming off it was black!

AutoGlym Fast Glass is pretty decent I find.

+1 for leaving AC on all the time - not only does it ensure windscreen stays clear it also prevents the drying of seals in the system and consequent loss of AC fluid, which is what the dealers keep trying to sell as a money making exercise.

But if I leave aircon on, then the stop/start doesn't work. I love my stop/start! Would leaving aircon always on, really increase fuel consumption that much?

But if I leave aircon on, then the stop/start doesn't work. I love my stop/start!

 

Then there's a fault with your car.

I keep the A/C on all the time (on AUTO), but I am not happy with the factory setting of the humidity sensor (MY 2014 Elegance).

Anti-fogging feature activates to lately and the windscreen becomes foggy from time to time in heavy rain.

I applied the VCDS trick and set the A/C to "hot countries". This cured the issue...

But if I leave aircon on, then the stop/start doesn't work. I love my stop/start! Would leaving aircon always on, really increase fuel consumption that much?

The a/c will only overide stop start if there is a high demand. On a cool day it won't be working that hard and will allow the car to sit at lights without the ac on for some time. If its El scorchio outside and you have only just got in the car then it may need to kick in or not stop the engine to allow the ac to keep cooling the car.

I applied the VCDS trick and set the A/C to "hot countries". This cured the issue...

Could you please post details of how to do this?

Could you please post details of how to do this?

 +1

Misting of windows has occurred in other makes I've owned,as with this one. My climate is nearly always on throughout the whole year, it also helps with keeping the air fresh on long journeys. Hence "aircon".

My stop start still works. Climate is set to medium.

Leave the AC on all the time, thats what it's there for.  Oh and keep in the inside of your windscreen clean.

 

+1 for what Neily03 said.

 

 

Leave the AC button pressed & the climate set to Auto.

This doesn't mean that the compressor is always active but allows the climate control unit to decide when its needed.

Also, if you have a heated screen this is an option in the vehicle settings to "Enable Automatic Windscreen Heating" which helps again.

Its been +35°C here for the last 2.5 weeks & my Stop/Start works just fine (except when you've only just get in the car & Ac is working hard).

 

 

If your car is relatively new, you will probably also have a foggy windscreen from the chemicals emitted from the dashboard plastics (which passes with time).

This is most obvious when the air is humid or its very sunny.

I had to clean my inside windscreen every 2 weeks for the first 6 months until it seemed to stop.

Keep your windscreen clean & you will see less fogging in damp conditions.