Hi,

 

I have question about the A/C temperature setting during the winter night time driving, and wondering could anyone share their tips to prevent the windscreen suddenly covered by fog while driving please.   I was driving on M3 last night, it was okay originally when I drove in lower speed before went on the mortorway.  However, my windscreen suddenly get covered by fog/ mist when drove in higher speed 70mph, it was a bit of panic and tried changing A/C setting to bring up temperature and switch to defog windscreen mode, but it just got worse and finally I had to open a gap of side windows to maintain windscreen visibility in very cold weather.  :(

 

My normally set the A/C to 19 ~ 20 degree while driving (winter & summer), A/C is always on and wind speed turned to 2 bars or 3 bars level (medium).  Recirculation was turned off, only use this during summer time when it is hot outside so cool air work efficiently inside the car. 

 

Will there be different scenario when moisture is higher either inside the car or outside the car?  Last night was pretty dry and not raining, so I think moisture inside the car was higher, but still couldn't figure our where I did wrong with the A/C setting.  Can anyone help please?  Thank you.

 

Cheers,

Luchia

 

How confident are you your recirculation command is working properly? Increased speed on the motorway will chill the windscreen more and then the inside moisture will condense. Scan to find faults or listen to the flap working (or not).

 

Auto setting works pretty well and controls both output directions and fan speeds.

 

And are your carpets wet at all anywhere - could this be the source of the moisture. Easy to miss a slow wet patch somewhere (including the boot).

I think I'm right in saying that the aircon on VAG cars switches off when the outside air temperature drops to 4 degrees or lower, to prevent the condensate from freezing.  I had this happen to me the other day when driving another car, a '59 Ibiza 1.4 - the windscreen suddenly misted up as you describe.  A quick look at the temperature and it had dropped to 4 degrees.  I must admit on my cars ('64 Toledo 1.2 and '03 Bora V6) the instrument panel does emit a warning noise when the temp drops like this, but I can't say I noticed the Ibiza doing so.

 

What was the temperature when you got onto the motorway?

5 hours ago, inspectorman said:

How confident are you your recirculation command is working properly? Increased speed on the motorway will chill the windscreen more and then the inside moisture will condense. Scan to find faults or listen to the flap working (or not).

 

Auto setting works pretty well and controls both output directions and fan speeds.

 

And are your carpets wet at all anywhere - could this be the source of the moisture. Easy to miss a slow wet patch somewhere (including the boot).

Good point that it could be the faulty recirculation flap, might need to check this out when doing the next annual maintenance.  Thanks for reminding.

 

I will also try the auto setting as well, I normally change it to manual mode as feeling the wind speed bit too strong on auto mode.

 

Inside capet should be generally drt, we did have some hot food inside the car, but it was alright when driving in low speed, so not sure the reason it suddenly got mist up when in high speed.

8 minutes ago, vwman55 said:

I think I'm right in saying that the aircon on VAG cars switches off when the outside air temperature drops to 4 degrees or lower, to prevent the condensate from freezing.  I had this happen to me the other day when driving another car, a '59 Ibiza 1.4 - the windscreen suddenly misted up as you describe.  A quick look at the temperature and it had dropped to 4 degrees.  I must admit on my cars ('64 Toledo 1.2 and '03 Bora V6) the instrument panel does emit a warning noise when the temp drops like this, but I can't say I noticed the Ibiza doing so.

 

What was the temperature when you got onto the motorway?

it was quite cold outside last night, temperature must be dropped to 1 to 2 degrees as I also heard the beep warning sound when it dropped under 4 degrees....

 

Have cleaned the windscreen inside out this morning again as some articles suggest dust/ dirty glass could be getting condensation easily, hopefully it won't happen suddenly again.