Misting up windscreen

[guest4761]

58 Plate Jazz 1.3 CVT SE.
If I run the car for 20 minutes or so normal motoring without the ac on, I find that the windscreen mists up if I close the air vent to the recirculating position. The vent would be in the closed position say in heavy slow moving traffic to eliminate exhaust fumes ingress. Any ideas please?

[culzean]

58 Plate Jazz 1.3 CVT SE.
If I run the car for 20 minutes or so normal motoring without the ac on, I find that the windscreen mists up if I close the air vent to the recirculating position. The vent would be in the closed position say in heavy slow moving traffic to eliminate exhaust fumes ingress. Any ideas please?

Recirculate does just that,  system keeps sucking stale moist air from inside the car and blowing it around back into the car to get even more moist and stale.   If you are going to use recirculate you really need to use aircon to dry the air -  It is not recommended to use recirc for any length of time as no fresh air getting into car (can cause you to fall asleep).  GD is prone to misting up anyway, even when set to fresh air position and even new cabin air filter would not cure it.

Also if you have had cold  air blowing up the screen and then turn aircon off the moist air hitting a cold screen can cause instant misting up,  especially if you choose recirc at same time.

[Jocko]

My Volvo automatically shut the air con off if you set it to recirc. I have my doubts that using recirc would have any effect on sending you to sleep though. For tens of years cars ONLY had recirc heating systems. However it certainly can cause the glass to mist up. You always carried a cloth or sponge in said old cars, to keep wiping the screen. And stick on double glazing to keep the rear screen clear!

[culzean]

My Volvo automatically shut the air con off if you set it to recirc. I have my doubts that using recirc would have any effect on sending you to sleep though. For tens of years cars ONLY had recirc heating systems. However it certainly can cause the glass to mist up. You always carried a cloth or sponge in said old cars, to keep wiping the screen. And stick on double glazing to keep the rear screen clear!

http://worldclassautoservice.com/use-cars-recirculation-button/

quote from a study in USA

The consistent recommendation from each of these studies has been to roll up your windows and use the setting to recirculate the air in your car when you are in heavy traffic or stopping frequently at red lights.26,27 Exposure with the windows open was more than six times greater than for pedestrians at a three or four way intersection.

While shutting the windows and recirculating the air in your car is important to reduce air pollution, in newer and more air tight cars you may experience a build-up of carbon dioxide. The car may begin to feel "stuffy" when two or more people are breathing the same air for an extended period of time.

Too much carbon dioxide in the car may also increase your experience of drowsiness, fatigue, confusion, headache and sleepiness.28 These are dangerous symptoms to experience while driving a car. To prevent this from happening, researchers recommend you pull in outside air for one to two minutes every 10 to 15 minutes to facilitate air exchange, while still minimizing over exposure to air pollution.29

Actually,  when weather is hot most cars will automatically switch to recirculate if you have auto climate control selected until the temperature inside the car reduces,  and if you choose 16 degrees (min temp on most cars) and it is 30 degrees outside it may stay on recirculate (whether there is a bleed of say 10% fresh air into system is another thing - but I assume there is,  modern cars are so airtight that if there was no fresh air bleed it could cause CO2 buildup especially with a car full of people).  Recirculating air means that the car AC system only has to deal with a car full of air and not keep sucking in hot air from outside the car and cooling new air all the time.

[d2d4j]

Hi

We use an old trick to keep moisture to a minimum

You leave in the car those bags that come with goods which take the moisture out

We have a couple of large bags which seem to help, but I do not think we suffer with moisture in our jazz yet anyway

Many thanks

John

[Jocko]

I used to find that on a humid day I would get misting on the outside of the windscreen when the air con was on and the system set to demist. At first I thought it was on the inside but the wipers would shift it!
Personally I have never found any of my cars particularly airtight. Draughts on a cold winter morning prove that.
In Scotland, setting your Climate Control to 16°C would see the heating on, for about 98% of the year!!

[MikeG1944]

Hi

We use an old trick to keep moisture to a minimum

You leave in the car those bags that come with goods which take the moisture out

We have a couple of large bags which seem to help, but I do not think we suffer with moisture in our jazz yet anyway

Many thanks

John

You can buy those bags specifically made for car demisting with up to a kilo of silica gel in them. Been using them for a few years now and can't remember the last time either of our cars misted up.

Mike.

[Jocko]

You can buy those bags specifically made for car demisting with up to a kilo of silica gel in them.

Just ordered two. Amazon, for under a tenner.

[VicW]

Another cause of misting can occur if the outlet vents for the car interior in the boot are obstructed.
These vent to the outside of the car allowing a through flow of air when not in recirculate.
They are located on the rear of the boot, just above the floor, in the cross member that the u-bolt for the boot locking catch is located.

Vic.

[guest6981]

You can buy those bags specifically made for car demisting with up to a kilo of silica gel in them.

Just ordered two. Amazon, for under a tenner.

Me too!