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Old 9th January 2012, 12:08   #16
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Default Re: Optimum techniques for defogging the windscreen

I summer especially during rains, both sides of the wind screen are fogged, so you use wipers for the out side and AC for the inside. If humidity is extremely high, the outer side will keep getting fogged due to AC, so you will need the wipers every now and then.

In winter till the windshield is heated up, it will fog, primarily on the inside (due to the hot breadth from our mouth), but if the humidity is high - as it is in Delhi now a days, even out side gets fogged. The heater may take time but it soon heats up the wind shield and gets rid of the fog on both sides.

As "sgiitk" has said, once your fundamentals of fogging are clear, you will take appropriate action to get rid of it.
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Old 9th January 2012, 12:22   #17
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Default Re: Optimum techniques for defogging the windscreen

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Originally Posted by dhanushs View Post
True, in some cars, heat is taken from the engine coolant. However, de-humidification is also one of the requirements for efficient defogging, and hence the compressor is switched ON.
Just need to be doubly sure, since I did not see my question answered. It's OK, right, if I switch the compressor on while the thermo is in the Hot zone?
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Old 12th January 2012, 19:11   #18
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Default Re: Optimum techniques for defogging the windscreen

^ Yep, it's fine to keep the compressor on, even if the temperature is set in the red zone. The compressor's functional is critical to keeping the glass defogged.
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Old 12th January 2012, 19:20   #19
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Default Re: Optimum techniques for defogging the windscreen

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Originally Posted by Samartha View Post
Just need to be doubly sure, since I did not see my question answered. It's OK, right, if I switch the compressor on while the thermo is in the Hot zone?
Yes, its OK for the compressor to be switched ON.

Well, even in manual AC's there is a certain grille temperature or fluid pressure, when achieved, the compressor cuts off. When the AC is in the heater mode, this does not happen, and the compressor is ON all the time.

Apart from this, there is no drawback. Also, considering the time used for defogging, the above mentioned procedure is just fine.
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Old 19th January 2012, 18:52   #20
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Default Re: Optimum techniques for defogging the windscreen

Use AC with the louvers directed to the windscreen - Best option.

Works better if the direct air [fresh air] mode is selected in non climate controlled cars.

Heater always takes a longer time to demist the windscreen and is not long lasting - guess its got to do with the humidity inside as well - experts pl clarify!
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Old 20th January 2012, 08:07   #21
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by dhanushs
Well, even in manual AC's there is a certain grille temperature or fluid pressure, when achieved, the compressor cuts off. When the AC is in the heater mode, this does not happen, and the compressor is ON all the time.
In the another AC related threads it is mentioned that "AC Compressor in diesel engined cars does not cut off (Knob in Blue Zone) even after the cabin is cooled (grill temp is reached).
Which of the above is correct?
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Old 20th January 2012, 08:48   #22
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Default Re: Optimum techniques for defogging the windscreen

What I do and has worked for me -
  • Keep the temperature knob in the midst of the red/blue zone.
  • Switch on the A/C / Compressor
  • Direct the air flow at defog mode as well as switch on the defogger

If there is too much condensation from inside, then the fan speed is increased, recirculate mode is switched off and temp is put in the max red zone.

Yet to use a cloth though and in fact it worsens and spoils the windscreen.
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Old 20th January 2012, 11:39   #23
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Default Re: Optimum techniques for defogging the windscreen

If the dew is outside, this is what I do:

1. Use the windscreen washer to clear the initial dew.
2. Put the wiper to slow intermittent mode to wipe the dew as soon as it forms again.
3. Drive fast. Airflow on the windscreen will clear it up.
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Old 20th January 2012, 12:08   #24
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Default Re: Optimum techniques for defogging the windscreen

I have seen Defogger liquid for sale in Singapore, not sure if its available in India. might not be useful on occasional fogging, but if you are planning to drive on a humid rainy day, its good to be ready and say 'Bring it on!!!'

PS: I didn't buy it just saw it.
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Old 20th January 2012, 14:31   #25
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Default Re: Optimum techniques for defogging the windscreen

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Originally Posted by Samartha View Post
How exactly does the defogger in higher versions clear up the windscreen. I reckon I'll need to follow the same sequence, but manually.

Much appreciate your advice.
In the Emotion pack version of the punto, the defogger button blows hot air at the windscreen and sets itself to fresh mode(air from outside).
It clears up the scree in 5-6 seconds and keeps lowering the temperature after that.
As a result, the windscreen remains clear.
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Old 20th January 2012, 18:08   #26
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Default Re: Optimum techniques for defogging the windscreen

In the winter its very simple to clear up windscreens.
First set the Air on recirculate and blowing on the windscreen from the (^^^) button.
Next put it on heat with AC switch ON.
As soon as the car heats up even a bit the windscreen will clear from inside.
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Old 21st January 2012, 12:05   #27
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Default Re: Optimum techniques for defogging the windscreen

I do two things which constantly keeps the windscreen clear.

1. I use the AC directed on the windscreen for 10-15 seconds which clears the foggy screen pretty fast.

2. Then I lower any one of my rear windows, only 1 inch or so. It does not fog after that as fresh air constantly keep the windscreen, as well as the rear glass free of fog. You can also use your heater if you prefer to.
Thereafter I do not need to use the AC or even rear defogger.

I would also like to mention that lowering 1 inch of window does not really discomfort the occupants.

This method also allows me to keep my attention on the road otherwise one tends to keep fumbling with AC/heater technique every few minutes.

The only time its an issue is in the monsoons, as keeping the window open is not an option, but it works great in winters. But in monsoons generally the outside of windscreen tends to fog, and its a pain to clear.

Last edited by ZeRo© : 21st January 2012 at 12:25. Reason: Changed clean to clear in the first line.
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Old 22nd January 2012, 15:05   #28
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Default Re: Optimum techniques for defogging the windscreen

It was a cold Bangalore morning, and we had the AC turned ON to clear the fog. The temperature was set to heating. (Not that cooling would not defog). A smallish stone from a lorry in front of us hit the windshield and it cracked. A small line which grew over 15 days period and now we have replaced it.

I guess, the impact on a heated glass made the difference. There were other occasions when the windshield was hit by stones, and it did not crack. There was once, a very big stone hit the windshield, and a deep crevice was formed on the glass, but nothing happened.

Not sure if the nature of impact, or the hot air onto cold glass made the difference.
But, Im sure next time, I will not blow hot air onto foggy windshield.
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Old 22nd January 2012, 15:37   #29
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by IndigoXLGrandDi View Post
In the another AC related threads it is mentioned that "AC Compressor in diesel engined cars does not cut off (Knob in Blue Zone) even after the cabin is cooled (grill temp is reached).
Which of the above is correct?
Hi, could you please point me to that thread?

I don't think there is any air conditioning system, that runs the compressor continuously.
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Old 22nd January 2012, 22:14   #30
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Default Re: Optimum techniques for defogging the windscreen

I do not have anything to substantiate this & hence I had never even mentioned. But I believe that blowing hot air onto the windscreen would result in a much higher temperature difference between the two sides of the glass & this in turn, makes the windscreen more vulnerable.

Quote:
Originally Posted by vinya_jag View Post
Not sure if the nature of impact, or the hot air onto cold glass made the difference.
But, Im sure next time, I will not blow hot air onto foggy windshield.
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