Sawe a post somehwere the other day where someone was complaining about steamed up windscreen...

Can anone help me with the following as I can't find the post!

1) Should I have recirc on or off to improve the situation?
2) Why does the aircon come on when you choose screen as the output? does my head in!

re-circ off... you want the air from outside.

I understand that but does that mean less steam ?

I never use the Air Con to de-mist the windscreen as you'll get more condensation in the car, because as soon as u turn the aircon off the screen mists straight up again, again I never use the Re-circulation button, have no need to.

I normally, just was 10 - 20 seconds with the air pointed at the screen, then its usually fine, having said that I rarely suffer from steamed up windows as I always have the air passing thru the car as it were.

It also helps demist if you have your windows open a little.

Get a room !! https://www.gamers-forums.com/smilie...milecrunch.gif

Best place to start is to clean the screen. The less crap there is on it, the less likely it is to steam up.

I never use the aircon to clear the screen as it steams up if you turn the a/c off and that's normally at 80mph on a crowded motorway.

AFAIK a/c shouldn't come on merely by selecting the 'screen only' output. Sounds like a non-UK feature, a mod or a wiring bolox.

Vindaloo.

a/c switches on automatically when I flick the dial to windscreen only on my UK 2002 WRX.

a/c on and off at this time of year does mean (for me anyway) condensation/no condensation at no specific intervals! I try and leave it off.

The aircon will come on when you select to demist the front screen because there is a switch on the back of the rotary dial. When the dial gets round to demist it makes this switch and so turns on the a/c.
You can disconnect the switch on the back of the panel if you wish to cancel this feature.

Dipster

When I switch mine to recirc I get more air blowing through the vents which helps demist the screen a little quicker. Just remember to switch back otherwise the whole thing mists up again while your driving.

Ok so basically I don't want recirc on ever (apart from when I drive past the sewage works M4 near Slough!) and switching to aircon when I select screen is normal, so just switch it off!

I did clear the screen - the reason for the Q is that when I left work yesterday in the rain it was fine, no steam. Parked it up for an hour at home and went back out, bloody thing had a stack of water on the inside!

Scoob dealer told me that quickest way to demist the screen is to put the Aircon and recirculate on, as you are introducing no new moist air into the car. It definitely works too.

But is does mist up again quickly when you turn off the a/c!

air con on when in re circ = dryer air in the cab.this works by reducing the temperature of thje air and the dew point reduces taking water out the air, by cooling it down. so far so good . so this clears the windows.
(switch off re circ and this will Reintroduce warm damp air and the water condenses out agAIN onto the window. DOH!!)
however i have found in practise if you leave air con on switch air temp to say 23 deg C then knock air con off after a few minutes windows stay mist free.
it is a bit dependant on other factors too.
a)are you wet?
b)is it cold and dry or warm and damp outside?
c)has the car got very cold internally?
So i guess really you have to fiddle about a bit and see what works for you.

It is all a question of Physics... bear with me!! (and sorry to all those that already know what I am about to write).

Condensation from the air forms on a surface if the temperature of that surface is below the "dew-point" of the air. Therefore, the best way to keep the surface (window) from misting up is to keep it above this temperature (hence just warm blower).

To confuse matters the "dew-point" temperature changes dependant on how saturated the air is, which is why it steams up more easily when there is more moisture around. This is why you do not want to recirculate, because you keep all of the moisture in the car.

All new cars (my old Clio sport and my 03 WRX) use the aircon to demist, because it works very well in the short term. However, as you have all noticed, when it goes off the window mists again. This is because the window has not been heated, so is still below the "dew-point".

Just a little something I learned from designing indoor swimming pools!!

I do not know if that helps or confuses!!

I really whish the Scooby had a Heated front screen like my old RS

My windows started to steam up, plus they would not clear which ever way around the dials were.

Then came a slight smell of hot water, OH dear the matrix had started to leak.

I might add, that when this started to happen I knew what it was straight away. The matrix had only just started to get damp, so the leak was minimal.

The windows were worse than those in a greenhouse, the only way around this for the next few days before it went in to be fixed, was keep the heater on cold.

Cost of repair £252.00

You can get heated screens for cars that didn't originally have them. I found one for my 306 for £190 on the web, but have lost the link now :(. Not sure how easy it is to wire them in though.

Idle- Another thing to check which seems to be common is that you haven't got a leak anywhere and you are holding water in the car.

My g/f's boot was letting in water which made matters worse everytime it was parked up. A quick glance showed nothing, but lifting the spare wheel up revealed a pond.

If your car is dry inside then initially use the blower with aircon to dry it then just drive with the blower on the lowest setting on a comfortable heat, with the vents open.