Author Topic: Aircon and windscreen clearing?  (Read 1257 times)

Vigman

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Aircon and windscreen clearing?
« on: September 12, 2018, 10:59:46 AM »
Hi

Still a Honda newbie so please bear with me!

I see that when you want windscreen clearing you have to have the slider to 'through stream' the dial to windscreen and obviously a hot temperature and fan BUT does it matter if the aircon button is on or off please?  I experimented and couldn't detect much difference?

TIA
Vigman

PS I had to have an aircon seal fluid put in by a specialist as it had dropped since the July refill but the gas sniffer could detect nothing from the condenser (which is in poor condition - 08 car but 25k miles)

ColinS

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Re: Aircon and windscreen clearing?
« Reply #1 on: September 12, 2018, 11:54:37 AM »
The reason heated air will remove moisture from the screen is not because it is hot but because it has lower Relative Humidity (RH).  Passing air through the aircon will lower it's temperature to such an extent that the RH goes over 100% and therefore it must lose moisture (hence the puddle under the car).  When it returns to ambient temperature it's RH is lower than it was before.

So the answer to your question is that aircon by itself will clear the screen and heating it will make it even more effective.

culzean

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Re: Aircon and windscreen clearing?
« Reply #2 on: September 12, 2018, 08:28:20 PM »
Having aircon on will always help clear moisture from screen, turning temperature up will make it even better. The hotter the air is the more water it can hold, and as ColinS says, the flipside is that the cooler air gets the less moisture it can contain which is why a cold night after a warm day deposits excess moisture as dew on you car and lawn ( or frost, depending on how cold the night is). The combination of aircon and heater works because aircon cools the air which makes it dump moisture and then heating this cold dry air up makes it super dry and eager to absorb moisture.


 When you have a dedicated screen clearing button in your car as mk2 onwards have, it turns on the aircon on and fan to full speed to clear screen as quickly as possible.
« Last Edit: September 12, 2018, 08:34:09 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

sparky Paul

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Re: Aircon and windscreen clearing?
« Reply #3 on: September 12, 2018, 10:01:48 PM »
You should be able to see the difference with the A/C on, ours clears the screen pretty fast with A/C on.

Engine has to be running, of course.

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