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Because when the sensor goes screwy I don't want my car to start flipping shit like the defroster on when it's not needed? Because manual controls make such automation totally unnecessary? Because even if the automated system were designed to be "fail safe", the state that's 'safe' is actually context dependent, therefore manual controls will be necessary anyway?

It ain't broke, so stop trying to 'fix' it.




The problem is the current solution doesn't work. Because trying to perfect those settings manually while driving in near zero visibility is scary and dangerous. And nobody even knows the correct settings to use! There are YouTube videos testing whether cold or warm air is the fastest way to defrost and/or defog your window, because nobody knows or remembers.

I honestly don't remember and my solution is "try both for a little bit while maintaining control of the car".


I just leave the defrost on when it's raining or cold regardless of whether my windshield is fogging. No need for an automated system and my windshield never fogs up.


it's really not that complicated, you just have to understand why condensation is happening in the first place. it's always because the glass is colder than the moist air it is touching. there are two strategies to deal with this: either blow air with very low relative humidity over the glass, or fix the temperature differential itself. if you're using the "blow dry air" strategy, you always want to turn on AC and at least some heat, as this will create low relative humidity.

now in the winter you can sometimes do better than this by fixing the temperature differential itself. you can either lower the windows or cool the entire interior by blowing air with no heat. in reality, most people don't actually want to drive around in the winter with windows down or no heat, so the best tolerable option is usually to do as above: turn on AC and heat.

in the summer you can also get fogging on the outside of the windows. just use your wipers for this.


>it's really not that complicated

After reading this I am still not sure which one to use. They seem to both work.


Both work, one is just faster than the other. The post you replied to seems to imply that cold air is better in the winter, but that is absolutely not my experience.

When I get in the car in the morning, the air is already cold. No amount of more cold air from the vents will clear that. What's making it fog up, is the moisture I'm exhaling. More cold air is not going to fix that unless I drive with all windows down. So the only reasonable option since AC don't work at low temperature, is waiting for the car to heat up.


tl;dr of my post: turn on AC and blast hot air at the windshield. if that doesn't work in the winter, open your windows. if it doesn't work in the summer, it's because the fog is on the outside of the windshield; use your wipers.


In my car there is a front window defrost button that turns on the a/c (to dehumidify) but also the heat. Dry warm air does the best to remove condensation.


Perfect the settings? I've never driven a modern car that can't do it perfectly well when you hit the demister button. You're well overthinking things.


Manual works just fine. I just drove clear across the Trans-Canadian Highway, east to west, in a car with manual controls and it all worked great. Your eyes stay on the road because sober people can reach out and grab objects, like knobs or buttons, without looking. If the matter of defrosting confuses you then maybe you should sit down in your car for five minutes and learn how the multi-ton machine works before attempting to operate it; you owe that much to the rest of society. Don't ruin a car just because you are too lazy to work a damn knob.

(Warm dry air evaporates water that's condensing on cold surfaces. That's very far from rocket science.)


One: I think we can discuss this without condescension for anyone who doesn't agree with you.

Two: You are making a false choice: Automatic settings need not replace manual ones. Essentially what we are talking about is a spot on the dial that says "auto" which you are free to not use, much like headlight controls on higher end cars.


In practice the introduction of high-tech options reduces the availability of the manual options as manufacturers seek to reduce costs. Touch screen AC controls don't supplement manual controls, they replace them. This leaves people without irrational infatuations with tech high and dry, hence why I'm annoyed at anybody who advocates for it. If you've been in the market for a new car recently you'd see what I mean. Considering the state of the automotive industry right now, I think my comment was gentle. The suggestion that defrosting windows should be a matter delegated to a computer because it's confusing made me roll my eyes so hard, I was nearly blinded.


But cars already have this. My 2014 Ford Edge has front/rear defrost/defog buttons and they work just fine. As "liability" said, the answer is warm, dry air which happily works for both the defrost and the defog requests.

Well, they worked fine, but my A/C just went out, so getting dehumidified air is a problem these days.


>It ain't broke, so stop trying to 'fix' it.

Sure, but the marketing department had to fill a few blanks in the "bad weather options pack" (optional but casually installed on all cars in production that will be available in the next six-eight months) for a mere US$ 3,000:

1) self-learning wipers (using AI to set automatically an appropriate wiping speed, including economode, that only wipes the right side of the windscreen when you make a free turn on right at a traffic light)

2) intelligent defrost (computing the correct defrost temperature through analysis of real-time satellite heat maps)

3) heated and ventilated mats (that can dry your wet shoes and lower half of trousers independently from heating/confitioning settings)


I hope you make an artistic statement and patent some of these awesome ideas. 1) for conversation starter purposes, and 2) so that we can make sure auto manufacturers never actually do this, or at least you get fabulously rich in the process...


Interesting this patent literally just expired today: https://patents.google.com/patent/US5412296


Expired in 2012, buddy.


oops, read that last line incorrectly, its more of a status than an event.


I'd rather have the AC system dehumidify outside air, then reheat it before blowing it on the inside of the windshield. Most car HVAC systems make AC and heat mutually exclusive.

Dry hot air to heat the windshield above the dew point avoids the "damned if you do, damned if you don't" choice of cold dry air to keep the inside from fogging up versus hot humid air to keep the outside from fogging up.

It's not a matter of temperature sensing on the windshield, but humidity sensing in the cabin air.




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