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Old 7th January 2012, 22:11   #1
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Unhappy Optimum techniques for defogging the windscreen

I'm new to this forum, so do let me know if I should be posting this query to a different sub-forum.

I own a Punto Active Diesel that doesn't have a single-touch defogging button. The AC and heater do a fine job on cold mornings/rain, but I have noticed the following:
  • If I switch on the AC pointed towards the windscreen, the windscreen clears up at a lightening speed. However, switching on the AC on a winter morning isn't that pleasant an experience.
  • The heater does a slower job of clearing the windscreen up. Also, the windscreen clouds up completely before clearing up. Plus, the heater becomes warm only after the car has been driven to some distance. I've heard that the heater simply diverts heat from the engine to the cabin, so that might have something to do with the delayed heating.
  • Once the AC has cleared the windscreen up, if I switch on the heater, the windscreen clouds up once again before it starts clearing up. However, if the windscreen was cleared up by the heater itself, the improved visibility is more longstanding.

I'd would want some advice from experts here as to what should be my protocol to clear the windscreen up. Also, 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.
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Old 8th January 2012, 10:08   #2
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Default Re: Optimum techniques for defogging the windscreen

Clearing the windscreen.

Is it on the inside or outside.

If Inside then the AC as well as the heater (outside air, heat if needed) work. Another trick is to use the AC in the outside air position.

If outside thenit will take longer. Heater on, full heat, outside air blowing at speed on to the windscreen.

This condition occurs when the temperature of the glass is lower than the dew-point. Inside gives near instant nirvana, while outside needs time for the glass to warm up. It is best avoided, and take corrective action as soon as you see signs of it.
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Old 8th January 2012, 12:38   #3
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Default Re: Optimum techniques for defogging the windscreen

If all you need is a quick start for your day to get a clear windshield, then keep a cloth with you. I usually wipe off the interior with the cloth (only on driver side), till the heater heats up from the engine heat. After that follow what @sgiitk suggested.
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Old 8th January 2012, 14:17   #4
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Default Re: Optimum techniques for defogging the windscreen

If your car has option to blow air on the wind screen then use that with heater in winter and AC in summer. For outside fogging use the wipers with water spray initially. Once the AC/Heater starts defogging the inside the outside will also be taken care of.

Some times in deep winter the side windows also get fogged up. Blow hot air on them, and the fog disappears (instead of windscreen only use the option for front + windscreen, in the blower control).

For rear screen, rear defoggers heater works the best. If as in my car you do not have them, use heater to blow air to the rear.

At times if nothing works, then a dry cloth is your best bet.
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Old 8th January 2012, 20:36   #5
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Default Re: Optimum techniques for defogging the windscreen

^^ I have had to go to my office quite early over the past couple of days, usually around 6AM. And no matter what I do, it always took a good 15 minutes or so for the glasses to clear up completely.

And at such junctures, the best bet as Aroy has mentioned is a dry cloth
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Old 8th January 2012, 21:11   #6
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by Samartha View Post
  • If I switch on the AC pointed towards the windscreen, the windscreen clears up at a lightening speed. However, switching on the AC on a winter morning isn't that pleasant an experience.
  • The heater does a slower job of clearing the windscreen up. Also, the windscreen clouds up completely before clearing up. Plus, the heater becomes warm only after the car has been driven to some distance. I've heard that the heater simply diverts heat from the engine to the cabin, so that might have something to do with the delayed heating.
  • Once the AC has cleared the windscreen up, if I switch on the heater, the windscreen clouds up once again before it starts clearing up. However, if the windscreen was cleared up by the heater itself, the improved visibility is more longstanding.

I'd would want some advice from experts here as to what should be my protocol to clear the windscreen up. Also, 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.

This is something that I wanted to ask for a L-O-N-G time... Looks like the heater does actually do its bit. What I wanted to know is whether the same technique can be used on rainy days / nights. I really dont like to use the A/C with (semi) wet clothes and wet hair but as I have all my windows rolled up, fogging on the inside becomes a real problem...... Specially in Bangalore during night time, when everyone on the oncoming lane uses high-beams, fogging, poor visibility and constant rain combined with the odd 2 wheeler who's just realized he needs to go across me and brake after overtaking me from the left .....
I have tried setting the heater .. but all it does is make things worse .. and the windshield clouds up completely.... Would the same techniques listed above work? I have ended up rolling the windows down many times because of this...
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Old 8th January 2012, 21:31   #7
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Default Re: Optimum techniques for defogging the windscreen

heater works best. If you use the ac, if the outside is cooler, you end up with condensation outside, and the wiper would end up only spreading it and making visibility worse, especially in cooler/night weather
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Old 8th January 2012, 23:28   #8
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by greenhorn View Post
heater works best. If you use the ac, if the outside is cooler, you end up with condensation outside, and the wiper would end up only spreading it and making visibility worse, especially in cooler/night weather
I beg to disagree. That was part of my question. I have realized that the AC works way faster to clear the inside of the windscreen that the heater. 10 seconds with the AC aimed at the windscreen and the inside clears up.

The heater works way slower. Also, with the heater, the windscreen clouds up first before clearing up.

But, like I mentioned, only the heater-cleaned windscreen stays clear in the longer one. The AC-cleared one clouds up as soon as I turn the heater on.

Using a cloth to wipe the inside of the windscreen works wonders as well.
Quote:
Originally Posted by vsathyap View Post
This is something that I wanted to ask for a L-O-N-G time...
...
...
Would the same techniques listed above work? I have ended up rolling the windows down many times because of this...
I'm afraid you'll find AC work faster in these scenarios than the heater. Unpleasant but fast.

Note from the Team-BHP Support Team: Please use the "edit" button if posting within 30 minutes of the first post, instead of creating another back-to-back post.

Also use "Multi Quote" option for quoting Multiple posts.

Last edited by Rudra Sen : 9th January 2012 at 10:36.
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Old 9th January 2012, 01:30   #9
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by vsathyap View Post
This is something that I wanted to ask for a L-O-N-G time... Looks like the heater does actually do its bit. What I wanted to know is whether the same technique can be used on rainy days / nights. I really dont like to use the A/C with (semi) wet clothes and wet hair but as I have all my windows rolled up, fogging on the inside becomes a real problem...... Specially in Bangalore during night time, when everyone on the oncoming lane uses high-beams, fogging, poor visibility and constant rain combined with the odd 2 wheeler who's just realized he needs to go across me and brake after overtaking me from the left .....
I have tried setting the heater .. but all it does is make things worse .. and the windshield clouds up completely.... Would the same techniques listed above work? I have ended up rolling the windows down many times because of this...
If your car has a/c; then turn on the a/c and set the temp. to hot and blower position to the windscreen. Also, select the air mode to outside air.

It should and it will clear the screen quick.

And defogger (if equipped) for the rear windshield.
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Old 9th January 2012, 02:17   #10
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Default Re: Optimum techniques for defogging the windscreen

Post deleted by the Team-BHP Support : Please do NOT post one-liners that add little or no informational value to the thread. We need your co-operation to maintain the overall quality of this forum.

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Last edited by GTO : 12th January 2012 at 19:09.
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Old 9th January 2012, 03:14   #11
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by libranof1987 View Post
If your car has a/c; then turn on the a/c and set the temp. to hot and blower position to the windscreen. Also, select the air mode to outside air.

It should and it will clear the screen quick.

And defogger (if equipped) for the rear windshield.
That brings me to the second question I've always wondered about. Does one really need the AC to be switched on for the heater to work? The heater, I reckon, simply redirects some of the engine heat to the main chamber.

In fact, some of my friends have advised me against switching on the AC when the thermo is set in the red zone. They say doing so might damage the AC apparatus.
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Old 9th January 2012, 09:05   #12
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Default Re: Optimum techniques for defogging the windscreen

+1 to libranof1987.

Turning on the AC but setting the temperature knob to hot (or midway between cold and hot) and directing air towards the windshield is the best way.

This way, the windshield gets defogged instantly and one is also not turned into frozen food!

Also, keeping the recirculation mode in "Fresh" avoids the suffocation that many of us generally feel upon using heated air.

Regards,
Jaspreet Singh
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Old 9th January 2012, 09:28   #13
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Default Re: Optimum techniques for defogging the windscreen

Everyday i see people with expensive cars cleaning windshield with hands or cloth or driving with windows slightly rolled down.

This is what works for me.

1)Direct airflow to winshield-defogging mode.

2)Switch on the blower and select desired speed.

3)Switch to fresh air intake

4)if driving in cold-set the temperature to the warmer side.

5)if you want the interiors to be warm and get rid of frost as well,direct the airflow to your feet and windshield
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Old 9th January 2012, 09:53   #14
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Default Re: Optimum techniques for defogging the windscreen

Folks, let us go back to the basics. When do you have fogging: When the surface temperature is lower than the dew point.

How do you fix it: Reduce the dew point (switch on the AC), or increase the surface temperature (hot air). Also, outside air is normally warmer (except in the winter chill) and normally has a lower vapour content.

Once you keep these basics in mind then you can evolve your own algorithm.
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Old 9th January 2012, 10:05   #15
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Default Re: Optimum techniques for defogging the windscreen

Quote:
Originally Posted by Samartha View Post
Does one really need the AC to be switched on for the heater to work? The heater, I reckon, simply redirects some of the engine heat to the main chamber.
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.
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