[buddenfan]

I was driving on the highway when my windshield fogged up. I pressed the Max button but it made it even more foggy for a good 20 seconds until it cleared up. I had to put my hazards on and slow the hell down.

Only time I ever have these issues was any bmw I ever had

[c1pher]

Windshields fog up easier whenever the inside of the windshield is not clean. You probably have offgassing VOCs on the glass you are not aware of. I’d simply clean it up and it should alleviate the issue to some extent, but that’s also why you have a defogger.

[buddenfan]

Originally Posted by c1pher

Windshields fog up easier whenever the inside of the windshield is not clean. You probably have offgassing VOCs on the glass you are not aware of. I’d simply clean it up and it should alleviate the issue to some extent, but that’s also why you have a defogger.

Yeah but the defogger fogs it more for 20 seconds until it slowly defogs and was a bir dangerous today hah

[c1pher]

Originally Posted by buddenfan

Yeah but the defogger fogs it more for 20 seconds until it slowly defogs and was a bir dangerous today hah

Are you in a humid climate? There may be a lot of moisture in the ducts that have to be forced out before the dehumidification can work.

[tranquility]

Are you vented to outside (good) and not recirculate? Also, weather-permitting, you may be 'forced' to switch on the AC.

[mcsquared]

In my experience, when that happens, turn to windshield mode and turn up the heat! It’ll evaporate the moisture on the windshield. Then, give the inside of the glass a thorough cleaning, every few weeks, and you should be good.

I have a ‘windshield wow’ that allows me to clean both the exterior and interior of the windshield at the same time. Helps a bunch.

[tracer bullet]

Originally Posted by tranquility

Also, weather-permitting, you may be 'forced' to switch on the AC.

Often the defrost does this automatically. Even if the light doesn't light up. I don't know about any particular car and can't guarantee but I do know it's the case for several previous cars I've owned.

I find that hitting defrost in either of my cars (both BMW) takes care of any fogging very quickly, just a couple seconds. I can't think of a case where it's been made worse.

[HighlandPete]

Originally Posted by buddenfan

I was driving on the highway when my windshield fogged up. I pressed the Max button but it made it even more foggy for a good 20 seconds until it cleared up. I had to put my hazards on and slow the hell down.

Only time I ever have these issues was any bmw I ever had

I'm assuming you were driving in wet conditions, to fog the screen.

Were you already running AC for dehumidifying, before it fogged with MAX? If not, there is your answer...

[tranquility]

Originally Posted by tracer bullet

Often the defrost does this automatically. Even if the light doesn't light up. I don't know about any particular car and can't guarantee but I do know it's the case for several previous cars I've owned.

I find that hitting defrost in either of my cars (both BMW) takes care of any fogging very quickly, just a couple seconds. I can't think of a case where it's been made worse.

Tx, maybe for some cars, but I don't feel any colder air when hitting the defrost. For sure that button works a lot of times but sometimes the foggy windshield is so stubborn I had to hit the AC as a last resort.

[buddenfan]

Originally Posted by HighlandPete

I'm assuming you were driving in wet conditions, to fog the screen.

Were you already running AC for dehumidifying, before it fogged with MAX? If not, there is your answer...

Rainy night

[tturedraider]

Did you have the climate system set to recirculate? Lots of folks these days use recirculate all the time. If you have the system on recirculate you MUST use the a/c to dry out the air. In the “old days” before all of the automatic hvac systems people kept the system set to fresh air. If you use fresh air in the winter or wet weather you will not get foggy windows. Setting the system to Defrost will automatically engage the a/c to dry out the air.

[Livetodrive]

If my windows are closed I keep the a/c on with recirculation off. The windows will not fog up with these settings.

[Mavus]

warm air to dry it out … it will take a min or two. do not blast cold air

[HighlandPete]

Originally Posted by Mavus

warm air to dry it out … it will take a min or two. do not blast cold air

That's the way we did it in the 'old days', before Climate Control.

But we do heat the cabin in the process. Using Climate Control with AC running in the background, no fogging at any time. Plus no heat or cold disturbances, due to having to manually intervene or interfere.

[tturedraider]

Originally Posted by HighlandPete

That's the way we did it in the 'old days', before Climate Control.

But we do heat the cabin in the process. Using Climate Control with AC running in the background, no fogging at any time. Plus no heat or cold disturbances, due to having to manually intervene or interfere.

I still run my hvac system completely manually, because I have never had an automatic system that could adequately deal with changing driving situations. So much depends on the sun. When bright, intense sun is shining on me the hvac system on automatic does not adequately adjust the cooling temperature or the fan speed. And on sunny cool/cold fall/winter days I may need warm air in the floorboard and cooler air from the upper vents. The key is the fresh air vs recirculating air. If you use recirculating air in cool/cold humid weather without the a/c you will get fogging 100% of the time. I use fresh air all winter (and summer) long and I never get fogging unless it’s maybe 98% humidity and then I engage the a/c to dry the air.

[Mavus]

Originally Posted by HighlandPete

That's the way we did it in the 'old days', before Climate Control.

But we do heat the cabin in the process. Using Climate Control with AC running in the background, no fogging at any time. Plus no heat or cold disturbances, due to having to manually intervene or interfere.

that does not work always in the northeast

[HighlandPete]

Originally Posted by Mavus

that does not work always in the northeast

What's the particular problem you encounter in the Northeast, which causes issues with full climate Control?

[Mavus]

Originally Posted by HighlandPete

What's the particular problem you encounter in the Northeast, which causes issues with full climate Control?

here is a specific scenario from 2w ago: 7:30am 70 deg outside and 99% humidity. Turned on auto hvac at 78 deg and cold air is coming out thru vents, was very slow to defog cabin windows. Turned off auto hvac and manually adjusted to 80 deg with front windshield defog ON and after 3-4 mins it was clear. Afterwords maintained temp on auto hvac at 75-76 deg was ok.

Another thing that happens is you could be driving from one area to another, such as valleys and hills, with changing microclimate unique to that area where conditions change within minutes. As an example Watkins Glen has its own unique microclimate.

The point is that when dealing with humidity in the cabin the quickest way to defog is to ensure warm air is blasting for a few mins and in my case I do that manually and it works every time. HVAC auto often blows cold air even if I increase temp setting.

[jmg]

Originally Posted by Mavus

warm air to dry it out … it will take a min or two. do not blast cold air

Air Conditioning on along with some heat will dehumidify faster than just heat. The act of conditioning air removes moisture from it. This is why in california winters above 40°C, I still run the AC, but combined with the heater.

[Mavus]

Originally Posted by jmg

Air Conditioning on along with some heat will dehumidify faster than just heat. The act of conditioning air removes moisture from it. This is why in california winters above 40°C, I still run the AC, but combined with the heater.

right that’s what I meant hvac on and higher temp setting

[HighlandPete]

Originally Posted by Mavus

here is a specific scenario from 2w ago: 7:30am 70 deg outside and 99% humidity. Turned on auto hvac at 78 deg and cold air is coming out thru vents, was very slow to defog cabin windows. Turned off auto hvac and manually adjusted to 80 deg with front windshield defog ON and after 3-4 mins it was clear. Afterwords maintained temp on auto hvac at 75-76 deg was ok.

Another thing that happens is you could be driving from one area to another, such as valleys and hills, with changing microclimate unique to that area where conditions change within minutes. As an example Watkins Glen has its own unique microclimate.

The point is that when dealing with humidity in the cabin the quickest way to defog is to ensure warm air is blasting for a few mins and in my case I do that manually and it works every time. HVAC auto often blows cold air even if I increase temp setting.

I take your first situation as a cold start up? If so, there won't be any initial hot air, whatever your temperature setting, auto or manual.

In similar start situations, which I also encounter here in the Highlands, I simply hit the demist button and leave auto settings alone. Same as I will hit the MAX button for a short time in heat, while leaving other settings alone.

As to microclimates, I see that all the time here in the Scottish Highlands, massive changes in temperature and humidity during the same trips. HVAC runs in the background with no issues at all.

Are you sure something isn't wrong, if auto settings (with AC running), can't prevent fogging and misting without intervention?

I had a VW Passat which would mist in some damp conditions. Car would also mist so easily, when stood over night. Problem was identified as water ingress, into the HVAC system. That solved, no further issues.

[tturedraider]

Originally Posted by jmg

Air Conditioning on along with some heat will dehumidify faster than just heat. The act of conditioning air removes moisture from it. This is why in california winters above 40°C, I still run the AC, but combined with the heater.

Correct. Just for clarity the air conditioning is what dehumidifies the air not so much the temperature. In particular if the hvac system is in recirculate mode. In recirculate mode the air conditioning is absolutely necessary to dry out the air. I run my system on fresh air virtually 100% of the time and virtually never have fogging issues. Defogging/dehumidifying/drying the air is the reason the air conditioner comes on automatically every time the windshield defroster setting is chosen.

With automatic hvac systems these days the system determines whether the air conditioner is on and it determines whether the air is set to fresh or recirculate. It chooses recirculate the majority of the time and as a result the air conditioner is also necessary. I only set my system to recirculate when the interior of the car is very hot and I turn on the air conditioning in order to cool the interior air more quickly. This also happens when you choose the Max cooling setting when the car is hot. The Max setting automatically sets the air to recirculate.

With so many folks just using the automatic system these days not many people understand the significance of the recirculate setting anymore.