Hazy and foggy windscreen issues while driving in rains

nRiTeCh

nRiTeCh

Skilled
When driving in rains esp. during late evenings and night times I'm facing the usual hazy/foggy issue on my cars windshield.

1723313759547.jpeg


The issue is severe at the left side than right and is happening to many cars- cars stuck in traffic, friends, families etc.

I did whatever Rnd I could and the haziness i mostly occurring inside/within the windshield is what I feel.
In standstill traffic, I saw drivers or the co-passengers stepping out of their cars trying to wipe off the fog and once in, the effect returns instantly. I too tried to wipe with a cloth from inside and it could not be wiped even 1% as it was not from inside. When I used vipers, it did help reduce the haze but only by 20% or so but not fully or to the max.

Its rather confusing as to whats the effect and where it is occurring as I'm 110% sure its not happening inside else using cloth I could have been able to wipe at least 1% of the fogginess!

**This issue somewhat also contributes towards traffic jams as well as one cannot judge the left-side and tries to maintain too much of a distance.

While I do not have a doubt about the functionality of AC, front and rear defoggers and blowers as they all are working just fine, I'm in search of the best combination of rain settings which can either get rid off this annoyance or at the most, considerably minimize to the best possible levels helping driving comfortably!

Its a struggle many of us face/and are facing since years across many car brands be it wagon r or a fortuner, yet everyone just keeps experimenting with the settings while not knowing which settings work guaranteed.

Even people on the almighty Teambhp aren't spared aka facing this issue.
www.team-bhp.com

Facing hazy windscreens during monsoon; How to get rid of it? | Team-BHP

BHPian 2000rpm recently shared this with other enthusiasts.Guys,Me and a lot of my friends with cars of multiple manufacturers and vintage are facing a unique issue in the Mumbai Rains.The windshield during ...
www.team-bhp.com www.team-bhp.com

Another issue of water gathering on all 4 passenger windows along with fog though it goes off with AC but a few solutions for that as well would be appreciated.

There are few products and methods available but I would primarily like to stick to the in-car air flow settings which should get rid of this annoyance naturally as thats how every car is designed with exceptions of a rear-viper.

--Thus, looking for a a single, simpler tried and tested technique which works across cars!
 
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What was the temperature of your AC when you took this picture?
Members of Team-BHP reply in a sensible way. Do one thing: post on any international car enthusiast forum, and you will get a similar reply.
 
I mostly do the following and never had problems.
  1. Set the fan mode to windscreen only.
  2. Set FAN speed to MAX.
  3. Turn AC ON, on the coldest setting. (once fog is gone you can adjust to your liking)
If fog is still preset, then I do
  1. Set the air circulation to external.
  2. Open windows slightly.
Fog is gone.
 
invisiblebond said:
What was the temperature of your AC when you took this picture?
Members of Team-BHP reply in a sensible way. Do one thing: post on any international car enthusiast forum, and you will get a similar reply.
Click to expand...
27-28c. Few suggested to use heater and not AC and bump it to the max 32c..haven't tried that yet.
Heisen said:
I mostly do the following and never had problems.
  1. Set the fan mode to windscreen only.
  2. Set FAN speed to MAX.
  3. Turn AC ON, on the coldest setting. (once fog is gone you can adjust to your liking)
Click to expand...
Tried 1-2 but the haze sits there..might reduce but keeps getting stronger and have to keep using vipers even when rains have stopped for a while or when extreme light breezing.
Haven't tried the 3rd option.

Heisen said:
If fog is still preset, then I do
  1. Set the air circulation to external.
  2. Open windows slightly.
Fog is gone.
Click to expand...
Haven't tried 1 but tried opening al 4 windows 20% down yet no impact!

Btw which car?
 
Heisen said:
Turn AC ON, on the coldest setting. (once fog is gone you can adjust to your liking)
Click to expand...
Warm air can carry away more moisture, so you need to increase the temperature if you have climate control. Not sure how manual AC works, so this might be applicable to those only. But making the glass too cold will definitely cause condensation both on the inside + outside.

nRiTeCh said:
Few suggested to use heater and not AC and bump it to the max 32c..haven't tried that yet.
Click to expand...
This is what I call "Turbo Mode" and required only briefly to clear heavy fogging.

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nRiTeCh said:
1723313759547.jpg
Click to expand...

is the same as this:
IMG_20240811_032231.jpg


Water vapour in the air is condensing on a cold object.
The car's AC is the problem as well as the solution to OP's problem.

Fogging on inside/outside of windshield, near the vents only (bottom of windshield):​

  • The AC temp is set too low. The glass has become so cold that moisture is condensing on the cold parts near the vents
  • Raise the AC temp to around the ambient/outside temp +/- 1°C (technically it should be above the dewpoint, which depends on temp + Relative Humidity, but external temp is a good/fast estimate)

If there is heavy fogging in a stopped car (AC off), use "Turbo Mode".
It works best once the engine is warm, since the heat comes from the engine coolant. If you had parked overnight and the engine is cold, this method won't work, so let the engine warm up first
  • Crack open windows
  • AC on
  • External air intake (i.e Recirculation off)
  • Temp to highest setting
  • Fan on Max speed
  • Airflow to Windshield vents
  • This should clear up the glass in seconds
Once the glass is clear, you can lower the temp to a more comfortable range, and redirect the airflow towards yourself aka Regular AC usage. For reference:
On warm nights I set temp to Ambient - 1 °C, airflow to face + feet, Fan on Auto, which will usually spin at lowest speed)
On cold nights I set temp to Ambient + 1 °C, airflow to face + feet, Fan on Auto, which will usually spin at lowest speed)
If you observe condensation slowly forming near the vents, simply increase the temp a notch.
Never switch off AC in rain/high humidity conditions: else the glass will fog up.


Fogging on outside of windshield, over a wider area:​

This may not actually be due to condensation at all, it could be:
  1. Streaking, where the wiper blades are old and leave behind a film of water. Replace wiper blades
  2. The washer fluid is too soapy, so it is leaving behind a translucent film: don't add too much soap concentrate to the reservoir. It should leave no residue at all
  3. The glass is extremely dirty with oily residue: wash it properly with soap + water, finish with IPA
  4. If none of the above works, your glass might have scratches that trap water, or scaling from hard water, in which case it might be easier to replace the windshield itself
In the TBHP link above, the haze pattern changes when the wiper moves over it, indicating it's on the outer surface.

Fogging on inside of rear glass:​

Just turn on the rear defogger. It uses electric heater wires to warm the glass and remove condesation.
Usually not too important. If the AC is running, it will take some time, but will eventually remove moisture from rear glass too


And for those who like to ride in the rain, get this and apply on the inside of your visor ;)
While this works on car too it makes no sense since you need to run AC anyway.
 
I'm also vistim of this phenomena. The following works for me
1. Set AC to Heater Max
2. Fan Speed MAX
3. Air intake set to exterior
1. Set AC fan towards front windscreen only.

After say 1 minute, glass becomes heated and fog completely disappears. Then do the following,
1. Set AC to Chill (2 or 3 fan), direction front & below
 
In addition to fog, condensation there is some kind of residue, stains on the windshield (outer) which doesn't go away with wiper or manual cleaning with cloth etc, appears when wet and diffuses stoplight and headlight of vehicles. Noticed during rains and its severe during night.
 
nRiTeCh said:
Also, is anyone using water repellent side mirrors?
Click to expand...
I've been using hoods for years. More effective at slow speeds/stand still. Recently applied Clear Vue, can't discern any improvement, probably since there's no airflow on the surface to carry the droplets away
 
Just understand the basics:

If there's moisture (humidity) in air,
And there's temperature difference between inside and outside of your car with one side having temperature lesser than dew point, it will fog on the side with moisture.

If it's cold outside, turning AC on with air going onto the windows will remove the fog immediately. Turning heat on will have worse effect.

If it's too cold inside, warmer air helps.


If temp on inside and outside is similar, it will not fog.
 
napstersquest said:
Just understand the basics:

If there's moisture (humidity) in air,
And there's temperature difference between inside and outside of your car with one side having temperature lesser than dew point, it will fog on the side with moisture.

If it's cold outside, turning AC on with air going onto the windows will remove the fog immediately. Turning heat on will have worse effect.

If it's too cold inside, warmer air helps.


If temp on inside and outside is similar, it will not fog.
Click to expand...
Yeah! Have to try few settings suggested here.
Thing is I'm uncertain as to how accurate is the temperature displayed on a instrumental cluster so that I can tune in the inside temps accordingly!
And this isn't an issue with me but several people out there incl. experts too. as everyone is on a trial and error method what works now isn't guaranteed to work in same situation later..
 
napstersquest said:
If it's cold outside, turning AC on with air going onto the windows will remove the fog immediately. Turning heat on will have worse effect.
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The defrost mode (windshield icon) will enable both AC and heater on simultaneously. The air first passes through the AC cooling fins, releasing moisture on it as condensation, then goes through the heating coil (a mini radiator through which engine coolant is allowed to flow when heater is enabled)

You can verify this by pressing the defrost button (windshield icon) and confirming the AC light comes on even if it was turned off previously. It should also automatically switch to fresh air (recirculation off)

AC off + heater on + closed windows will cause heavy fogging since warm air can carry a lot of moisture which inturn will enable dewing at higher temperatures. You need AC to actively remove the moisture that people inside the car are adding to the air with every breath.

(Sorry for the walls of text. Check the car's manual for detailed info about when to use each mode)

nRiTeCh said:
Thing is I'm uncertain as to how accurate is the temperature displayed on a instrumental cluster so that I can tune in the inside temps accordingly!
...as everyone is on a trial and error method what works now isn't guaranteed to work in same situation later..
Click to expand...
Accuracy doesn't matter: temperature is only one variable, without the ability to track inside
humidity level, you will have to try various settings and find what works. The simple logic is if it is fogging with AC on, increase the temperature

If the car has stopped, the external temperature reading will be higher since the sensor is located in the engine bay, so check after a couple of minutes of driving
 
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