Windows keep misting up.

-Rich- · December 2, 2016

This is driving me around the bend now, I have to keep the aircon on all the time otherwise the windows fog up.

I have done the usual of checking the pollen filter, under the mats to make sure it's dry and checked all of the boot, which is dry.

Does anyone else get this, what can I do to stop it? Surely door seals can't be gone on a 5 year old car.

NemesisUK · December 2, 2016

I've always kept the a/c on in all my cars, summer and winter. This dehumidifies the incoming air and keeps the interior free of damp and the windows clear. Even says to do so in the owner's handbook. In some systems (not sure about Lexus) it's recommended as it keeps the system seals lubricated, preventing leaks.

BTW - I've never seen a negative impact on mpg.

doog442 · December 2, 2016

Is you air button switched to 'outside' ?

You aren't recirculating I take it ..? if not, is the car misted up first thing in the morning ( and if so and its happening more often than not) then you must have water incursion somewhere...or are you carrying damp gear..my golf equipment caused this issue.

stormchaser · December 2, 2016

It's inevitable in this weather. Mines 5 years old too but I just keep the AC on which as said dehumidifies the car.

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The-Acre · December 2, 2016

Interestingly this subject comes up every year at this time. There's something about the change in the weather in November/December that causes this. When we get to about January it seems to be less of a problem, no idea why.

Zotto · December 2, 2016

It may be useful , with AC on, keeping windows clean using a good windows cleaner (foam type?); also a little bit of grease on glass contributes to make mist.

floggit · December 3, 2016

Always thought the reason for condensation was different temperatures on either side of glass. With heater on then parking the moisture in the warmth of air in the car cools and forms condensation. I always turn heater off 5mins from home and open a window to balance temperature on either side of glass. Yes its cold and not ideal but i dont get condensation very often.

NemesisUK · December 3, 2016

27 minutes ago, floggit said:

Always thought the reason for condensation was different temperatures on either side of glass. With heater on then parking the moisture in the warmth of air in the car cools and forms condensation. I always turn heater off 5mins from home and open a window to balance temperature on either side of glass. Yes its cold and not ideal but i dont get condensation very often.

That's the science of it, a cool surface condensing water vapour. But if one operates the a/c there is very little water vapour in the incoming heated air and generally within the vehicle. Parking up overnight there will be a degree of condensation, depending on temperature differences and humidity levels but once the a/c starts up this clears quickly. If condensation is a major problem then one should look to making sure things like scuttle drains are free from blockages (leaves etc..), carpets aren't wet from leaks or overflowing drains. Check also the underneath of the carpets, the sound deadening layers as sometimes the carpet surface is dry but the underfelt is sodden.

PCM · December 3, 2016

I have the blower on feet/windscreen, use the 'clear window' option when I start up, as it clears use the A/C, and use one of the damp-bags overnight ... with the re-circ off.

colin79666 · December 3, 2016

I keep a couple of those microwavable bags in the door pockets which helps a little to drawn moisture out. I usually find the windscreen has fogged up a bit overnight but nothing extreme and it soon clears with a blast from the AC (which I tend to leave on auto). From the cars I've had the worst have definitely been those with the most raked windscreens.

-Rich- · December 3, 2016

It's fine overnight and clear in the morning but as soon as you start the car the windows fog up. It's not condensation, the glass isn't wet. I also place one of the dehumidifier bags in the dash.

Once the quick clear has finished we have to leave the aircon on to keep the glass clear. It's always on recirculate unless it's switched over automatically to fresh air.

I know it's expected abit in this weather but my other cars don't really do it compared to how bad it is in the CT. Within seconds of turning off the aircon all the windows are fogged up.

I've not given them a good clean yet so will try that and see if it helps.

NemesisUK · December 3, 2016

Have you checked the cabin air filter?

200h · December 3, 2016

hi rich

now dont laugh ....

if you have a hot drink before you leave for work in the morning i have found your hot breath

will mist the windscreen in seconds so i now wait until i reach work.

stormchaser · December 3, 2016

Very true that. Body heat/breath and a cold car = steamed up windows instantly.

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doog442 · December 3, 2016

7 hours ago, -Rich- said:

It's always on recirculate unless it's switched over automatically to fresh air.

That's your problem.....don't have it on recirculate as per my post above.

NemesisUK · December 3, 2016

1 hour ago, stormchaser said:

Very true that. Body heat/breath and a cold car = steamed up windows instantly.

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That's why I always breathe through my nose when sitting in a defrosting car, seems to help ;)

200h · December 3, 2016

its ok to have the car set on recirculate but only use this mode for a short period of time,

using this mode to demist with AC on is good,and in the summer having recirculate turned

on will help to cool the car quicker, the tell tale signs that recirc has been on for too long

is that your windscreen will slowly start to mist at the bottom and / or the rear window will

mist up as soon as you see these signs turn the recirc off.

Wass · December 4, 2016

17 hours ago, 200h said:

its ok to have the car set on recirculate but only use this mode for a short period of time,

using this mode to demist with AC on is good,and in the summer having recirculate turned

on will help to cool the car quicker, the tell tale signs that recirc has been on for too long

is that your windscreen will slowly start to mist at the bottom and / or the rear window will

mist up as soon as you see these signs turn the recirc off.

I agree, irrespective of cabin filter, fresh air seems to cure the issue.

DanD · December 6, 2016

You should never leave it on recirculate, and should leave it on Auto to do what it's supposed to do.

Recirculate is only supposed to be used for short periods of time to either quickly cool or warm the car (in conjunction with the aircon), or if you are in a tunnel or following a polluting vehicle. Not sure about the CT, but the RX manages this automatically.

NemesisUK · December 6, 2016

As does the RC

TwitchyArmadillo · December 8, 2016

I leave the a/c on most days. Although I sometimes crack open the windows for a quick breeze. For a lot of modern cars I find that it's no longer correct to think of the a/c as just a method for cooling the cabin. My Nissan used to refer to this as environmental controls. The a/c was crucial for maintaining the air quality, temp and screen misting. Both my Nissan and CT don't seem to lose mpg with the a/c on. Don't forget that with the car in ECO mode a lot of the fans etc are actually toned down to conserve power.

-Rich- · December 8, 2016

On 12/3/2016 at 1:26 PM, NemesisUK said:

Have you checked the cabin air filter?

Yes I checked that and it looks fairly new, which it should be cos it was serviced 3 months a go.

On 12/3/2016 at 8:19 PM, doog442 said:

That's your problem.....don't have it on recirculate as per my post above.

I probably exaggerated about that, it's not on constantly but I do have a habit of switching it back over as it does clear the windows quicker.

On 12/6/2016 at 2:09 PM, DanD said:

You should never leave it on recirculate, and should leave it on Auto to do what it's supposed to do.

Recirculate is only supposed to be used for short periods of time to either quickly cool or warm the car (in conjunction with the aircon), or if you are in a tunnel or following a polluting vehicle. Not sure about the CT, but the RX manages this automatically.

The dealer did mention that actually, it does sense if there is a polluting car in front and will switch it over automatically.

2 hours ago, TwitchyArmadillo said:

I leave the a/c on most days. Although I sometimes crack open the windows for a quick breeze. For a lot of modern cars I find that it's no longer correct to think of the a/c as just a method for cooling the cabin. My Nissan used to refer to this as environmental controls. The a/c was crucial for maintaining the air quality, temp and screen misting. Both my Nissan and CT don't seem to lose mpg with the a/c on. Don't forget that with the car in ECO mode a lot of the fans etc are actually toned down to conserve power.

We've only had the car just over 2 months so I haven't been able to gauge if it loses mpg with the air con permanently. In my Accord I leave it on all summer and it does affect it a little, but then that does 20mpg around town so I always try to save fuel when I can!

NemesisUK · December 8, 2016

I left the a/c on all the time in my CLS and that did 12mpg around town, turning the a/c made no difference, except to make me rather warm and sticky!!

DanD · December 20, 2016

Air con units are a lot smaller and far more efficient than they used to be. My teenage son has a Peugeot 107 with a one liter, 3 cylinder engine that gives out 70ps and even in such a small car having the aircon has little impact on performance and consumption.

adnewton · December 20, 2016

You need to leave HVAC in Auto. It will then decide what is needed via numerous sensors in cabin. If you manually switch to recirc air, your windows will mist up.

Use quick demist function until cleared, then switch back to Auto. It the most efficient way of keeping cabin warm/cool and mist free.