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Old 22nd January 2012, 22:57   #31
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Default Re: Optimum techniques for defogging the windscreen

@dhanush
The link is
http://www.team-bhp.com/forum/techni...-not-trip.html (Air-con compressor in a diesel car does not trip?)
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Old 23rd January 2012, 10:19   #32
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Thumbs up Optimum techniques for defogging the windscreen

Why fogging happens:
When the temperature outside the car is colder than inside the car, the water vapor(humid) inside car gets condensed as water on the window. This is similar to the effect of water deposit on a cold water bottle taken out from the fridge. Water vapor is created inside car due to various reasons. One of the main reason is our breathing.

So there are two ways to remove fogging:

Easy practical fix:
Remove the humid inside the car by switching on the AC. It doesn't matter whether AC is on heating mode or cooling mode. AC has inbuilt mechanism to remove humid content from the air it circulates. Keep the blower to the window until fog is cleared and change the direction afterwards. As long AC is kept ON it is less likely that fog can deposit again.

Caution: Keeping AC in cooling mode + blower directed towards the window for a long time can cause outside deposit of fog.

Alternative fix:
Bring the window to a temperature which is more or equal to the inside temperature of car and maintain it. This can be done by setting the fan to heat mode and switching off AC. This will take time as the glass has to get heated by the air. But there is a problem here. The humid inside the car is not removed. So you may feel suffocation after some time.

What I would dream from the car manufacturers sometime in future is, an explicit humid remover cum air purifier which can be switched-on independently while AC is still kept switched off.

Last edited by SANSI : 23rd January 2012 at 10:40.
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Old 23rd January 2012, 13:15   #33
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Default Re: Optimum techniques for defogging the windscreen

Here's what I have been doing this winter. Car is first-gen Swift diesel.

1. For the first 3-5 mins the car's windows don't get fogged up so I do nothing.
2. As soon as there's first hint of fog on the front windscreen I switch the blower on with knob turned 100% towards hot zone in windscreen only mode.
3. The blower still doesn't throw really hot air as it should at 100% red but the engine is warming up and whatever hot air it throws is enough to de-fog the windscreen.
4. Now this continues for a few mins after which the hot air from the windscreen starts bothering me as the hot air blows through my forehead/face and hair which is not a very pleasant feeling. To add, both the rear door windows fog up badly, which affects my quick head-check movement used when changing lane. By this time the hot/cold knob is also at a 75-80 degree angle, towards red. Its like 2-3 clicks towards red from middle.
5. So I move the blower from front windscreen to upper cabin area only, this is the best mode as it keeps the both rear windows clear of fog, but only for sometime as now the front portion of the front door windows starts fogging up which makes it hard to see traffic through both the ORVMs. The front windscreen remains clear though.
6. So I again move it to front windscreen mode which de-fogs the front door windows, only to move it to previous position when the rear windows fog up.

This is the game I have to play a couple of times when going to office and coming back in the 1 - 1.5 hour journey, one side, everyday.

Best solution for me would've been a mode where both the front windscreen along with upper cabin area would be in air-throw mode. However, along with windscreen the only other mode available is lower cabin area / towards our legs.
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Old 23rd January 2012, 15:22   #34
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Default Re: Optimum techniques for defogging the windscreen

To demist the front side windows, direct the hot air from the front side vents towards the window. Blowing hot air up in fresh air mode, once the wind shield and front windows are clear, keeps all the windows clear.

Last edited by Aroy : 23rd January 2012 at 15:26.
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Old 24th January 2012, 12:35   #35
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by Aroy View Post
To demist the front side windows, direct the hot air from the front side vents towards the window. Blowing hot air up in fresh air mode, once the wind shield and front windows are clear, keeps all the windows clear.
I can't believe I never thought of it!!

I've been in habit of keeping the side vents closed for so long now that I almost forgot they are right there to take care of this issue.
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Old 24th January 2012, 21:20   #36
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Default Re: Optimum techniques for defogging the windscreen

Just wanted to share that I've been successfully following the method suggested by a helpful poster in this thread: Keeping the compressor on in the heater mode, and it works wonders. The windscreen clears up almost immediately and doesn't fog up thereafter.

One variable less in life. :-)
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