Steamy windows

[hobbes748]

Good morning folks. This is my first post since joining you, so please go easy on me...

I'm experiencing some strange fogging/misting/condensation (or whatever you want to call it) on the inside of the windscreen on the colder mornings. I get in the car and everything is fine and dry, but after only a few hundred meters of driving the screen suddenly mists up to the point where I have to pull over as I can't see a thing. A minute later, the condensation is away again and won't re-appear until the next cold morning.

Other than on cold mornings, the car never suffers from condensation inside the cabin.

It's a 2004 diesel exec.

I don't suspect a leaky heater matrix (carpets are dry, windscreen is spotlessly clean and the cabin is odourless).

I'll check the pollen filter, but I don't really suspect that either.

It wouldn't bother me so much if I could just sit in the car for a minute or two until it's done it's de-mist thing, but the condensation does not appear until after I move off. So I have to get in the car, drive it to the end of the road, park it (badly, as I can't see a thing), wait a minute, then drive off again.

The car doesn't suffer from misting at any other time.

I vaguely remember reading something about the climate control doing something differently below certain temperatures, but can't remember what, where I read it - or if it's true. Any help in working out why it's doing this (and how to stop it) would be greatly appreciated.

Many thanks

 

[Mr Honda]

Usually the pollen filter is the culprit for foggy front windows, but the window demister button is there for a reason anyways too

 

[hobbes748]

Usually the pollen filter is the culprit for foggy front windows, but the window demister button is there for a reason anyways too

Thanks for the reply, but I can't see why the pollen filter would be the problem only on cold mornings - and only while I'm in motion. Above about 4 or 5 degrees there's never any misting issues.

As for the de-mister button... I've tried it and, initially, all it does is make the window steam up faster.

 

[Mr Honda]

Weird!! :huh: :huh: Has the windscreen ever been replaced in it, could be dodgey seals or something, and as for the demister button making things worse, maybe your air con needs a re-gas?? Check the pollen filter now if you can though, when was the last time it was changed?

 

[hobbes748]

Weird!! :huh: :huh: Has the windscreen ever been replaced in it, could be dodgey seals or something, and as for the demister button making things worse, maybe your air con needs a re-gas?? Check the pollen filter now if you can though, when was the last time it was changed?

You're not kidding it's weird! I think it's the original screen (getting a bit scratched now), but it's certainly a genuine Honda one. That's the thing - the car NEVER steams up at any other time. Not when it rains, not when I'm dripping wet after walking the dog in the rain - never. It only happens after I've pulled away on a cold morning.

The aircon was serviced and re-gassed in August.

Dunno when the filter was last changed. I've had the car since May and although it's got full service history - it's independant history, so no idea when it was last changed. Can I try running without it to see if it makes a difference or will I just blow air out through my glovebox if I do?

 

[tbourner]

Mine does it if I've turned from 'auto' to 'off' on the climate control just before stopping, probably because it leaves the vents in the previous location meaning when you're moving you get air recirculating or something and coming up through the top vents.
Just hit 'auto' as soon as you've started the car, set to 21 and go.

 

[tbourner]

I vaguely remember reading something about the climate control doing something differently below certain temperatures, but can't remember what, where I read it - or if it's true.

Also, the hot gas heater system is voodoo.
I think it only works below 0 degrees, and only when you have 'auto' on and set to 'Hi' temp. Or at least that's what people have said in the past, there doesn't seem to be any real info on it.

 

[hobbes748]

Mine does it if I've turned from 'auto' to 'off' on the climate control just before stopping, probably because it leaves the vents in the previous location meaning when you're moving you get air recirculating or something and coming up through the top vents.
Just hit 'auto' as soon as you've started the car, set to 21 and go.

The car is usually set on 'auto' and 22. It happens then. Tried it with 'auto' off - still does it.

Didn't know about the hot gas thingy. What I'd read was something about the aircon either being unable to switch on (or off) below a certain temp. I can't honestly remember and at the time it didn't realy interest me. I should really start paying attention a bit more.

 

[OB1]

Steven, it does the same on mine and I often have to pull over too. It made no difference changing the pollen filter. I don't think it helps by introducing a nice warm person breathing warm air into a cold car so I just hold my breath for a few minutes till the aircon does its stuff.

Welcome to TA btw.

 

[Gaz172]

Have you tried cleaning the windows?

 

[vile]

Try cleaning the inside of the window with an anti mist cleaner by rain x it works very well but not cheap.

http://www.ehow.com/video_4997521_rain_x-defogger-liquid.html

 

[hobbes748]

Have you tried cleaning the windows?

Yup. Windows are squeaky clean.

I pulled the cabin filter out this evening and..... it looks fine. Almost as good as new, so it must have been replaced with it's last service. I'll order up another, just in case, but I'm not holding out much hope it's that which is causing the problem.

 

[Doc]

Your windscreen steams up because you breathe! The warm breath you exhale condenses on your cold windscreen. Short of holding your breath you can't stop it. The diesel engine is very efficient so heats up quickly. The warm air coming out your vents has the same effect as you breathing. Once the windscreen warms up the condensation stops so the screen clears.

Things such as making sure the inside of your screen is clean will help reduce the problem but short of not breathing you can't stop it. Or give yourself a bit more time before you set off in the morning to allow your screen to clear. If the cops see you driving with a misted screen they can pull you over and fine you.

 

[vile]

Your windscreen steams up because you breathe! The warm breath you exhale condenses on your cold windscreen. Short of holding your breath you can't stop it. The diesel engine is very efficient so heats up quickly. The warm air coming out your vents has the same effect as you breathing. Once the windscreen warms up the condensation stops so the screen clears.

Things such as making sure the inside of your screen is clean will help reduce the problem but short of not breathing you can't stop it. Or give yourself a bit more time before you set off in the morning to allow your screen to clear. If the cops see you driving with a misted screen they can pull you over and fine you.

Matt is correct i got stopped a few years ago and was told off for having to much ice on the screen in winter

 

[hobbes748]

Your windscreen steams up because you breathe! The warm breath you exhale condenses on your cold windscreen. Short of holding your breath you can't stop it. The diesel engine is very efficient so heats up quickly. The warm air coming out your vents has the same effect as you breathing. Once the windscreen warms up the condensation stops so the screen clears.

Things such as making sure the inside of your screen is clean will help reduce the problem but short of not breathing you can't stop it. Or give yourself a bit more time before you set off in the morning to allow your screen to clear. If the cops see you driving with a misted screen they can pull you over and fine you.

Thanks Doc, but I'm still breathing when the car is stationery, and it doesn't steam up then.

If I start the car and drive off - it steams up about 200m down the road
If I start the car and sit in it for 5 minutes, it's fine (it doesn't steam up). But as soon as I drive off, it steams up about 200m down the road.

 

[Jon_G]

I'm wondering if the drain pipe from your aircon system is blocked? With the aircon running on full cold, do drips of water come out of it?

PS - a big (and important) difference between warm breath from occupants and warm air from the blower is the relative humidity... warm breath is almost completely saturated with moisture, while cold air drawn in by the ventilation system and then heated has a very low humidity content. So the former will tend to steam up the windscreen, while the latter will tend to clear it.

 

[Jon_G]

...or maybe your ventilation system is stuck on recirculate?

 

[OB1]

If I start the car and drive off - it steams up about 200m down the road
If I start the car and sit in it for 5 minutes, it's fine (it doesn't steam up). But as soon as I drive off, it steams up about 200m down the road.

Your warm, moist breath condenses on a cold windscreen, causing it to mist. Starting the car and sitting in it a few minutes will warm the windscreen so your breath doesn't condense so much on it. As soon as you move off, the car is moving through the cold air. The windscreen cools again. Your breath is now relatively warm (and moist) compared with the screen so it condenses, misting the screen up.

 

[tbourner]

The car is usually set on 'auto' and 22. It happens then. Tried it with 'auto' off - still does it.

You might have a problem then.
When you're driving the air comes through from outside and out the vents, hence why I said it does it on mine if I've turned off 'auto' when stopping the car, cos it must have been on external air whilst on auto - especially around this time of year when it doesn't need to cool or heat the air too much to get to the set temp. When I get the problem I just hit auto again and it goes in like 5 seconds, so sounds like your 'auto' function isn't adjusting the diverter valve thingies in the pipe system properly, and they're stuck on external air.
Have you tried setting the air con yourself? Set it to recirculate, or try just pointing it at your feet or something, leave it like that for a week or so and see if it still does it.

 

[vile]

Guys I find if you turn on your front screen cold air this clears it very quick as it uses air con.
But then if you turn it off the screen will fog up very quick.
I don't no why this is but this used to happen on my 7th gen as well.

 

[hobbes748]

Thanks guys! You've given me quite a few pointers which I'll work my way through.

I've got a couple more questions relating to your suggestions...

When I hit the re-circulate button the system moves from 'auto' to manual. Is that normal?

How would I check if the car is stuck on re-circulate?

Where's the air-con drain hole/pipe? I'm doing an oil and fuel filter change tomorrow so will be under the car, so if someone can tell me where to look I'll see if there's anything amiss or blocked then.

Thanks again for all your help.

 

[tbourner]

If you change any settings yourself it should turn off the auto function.

I think if you look under the front of the car, it's the only clear hose end you can see hanging down - looks like something that's popped off and shouldn't be there, quite scary if you don't know what it is and water's coming out!