Windscreen mist

[Kaz117]

Hi all,

As you know its especially cold right now in the UK, incredibly so in Scotland.
I've just bought my Roadster a few days ago, and today I've noticed the misting is really bad in between the layers of the windshield, but only on the driver side! How convenient!

Has anyone else experienced this? I tried to wipe it off inside and out, but I'm sure it's in the layers, I assumed the windscreen was just 1 layer of glass though. Maybe its just from my breathing in the cold since its on my side only?

It disappeared after driving for 5 mins, but it really was dangerous with the sun glaring into it, obscuring everything.

Edit: The demisters were on, but engine was cold and AC off.

Thanks

 

[Rudyrov]

We use heat and defrost functions, a combination of Air Conditioner and heat functions in the US for areas where the windows get very foggy on cold mornings.

 

[bmwz3tower]

I've found that even if the water temp dial is in the middle it won't demist, I've got to drive it for there to be enough heat, but I don't have ac so it's probably a little different

 

[Rudyrov]

Ac removes moisture, it sort of blows out "DRY" air and that removes moisture, at least that's how I understand it.

 

[Grumps]

As above, use the A/C until it clears

 

[Jam03]

If the car is up to temperature and the heater works and is blowing warm air onto the inside of the screen, it should clear whatever is on the inside before too long. If it’s warm inside the car and you’ve wiped the inside and there’s still something obscuring your view there’s a serious problem with the windscreen, or you’ve wiped it with an oily rag. It’s not uncommon for Z3’s to be a bit damp on the inside, so ice forming on the inside of the windscreen in really cold weather wouldn’t surprise me, but what you’re describing is unusual.

 

[Pond]

As above, use the A/C until it clears

The only problem with using the A/C and heat in cold weather is that, although it does get rid of moisture quickly in the car, the moisture can stay on the a/c evaporator when the car is switched off, then evaporates back into the car again, rather than draining away to outside as a liquid.

Shutting the 'recirc' flaps to the fan does help, as it prevents fresh, damp air from entering and increasing the problem.

 

[Pond]

Ac removes moisture, it sort of blows out "DRY" air and that removes moisture, at least that's how I understand it.

Yes, sort of. Any refrigeration system inherently de-humidifies, as the evaporator temperature is always below the 'dew point' of the air, so moisture from the air going over it is condensed out into liquid water.

 

[Kaz117]

If the car is up to temperature and the heater works and is blowing warm air onto the inside of the screen, it should clear whatever is on the inside before too long. If it’s warm inside the car and you’ve wiped the inside and there’s still something obscuring your view there’s a serious problem with the windscreen, or you’ve wiped it with an oily rag. It’s not uncommon for Z3’s to be a bit damp on the inside, so ice forming on the inside of the windscreen in really cold weather wouldn’t surprise me, but what you’re describing is unusual.

Just to be clear it did go away while driving, just within first min or 2 while driving before the engine was warming up.

 

[Hwk-I-St8]

The only problem with using the A/C and heat in cold weather is that, although it does get rid of moisture quickly in the car, the moisture can stay on the a/c evaporator when the car is switched off, then evaporates back into the car again, rather than draining away to outside as a liquid.

Shutting the 'recirc' flaps to the fan does help, as it prevents fresh, damp air from entering and increasing the problem.

In Iowa, where temps can reach -20F (-28C), putting the hvac system on "recirc" is the worst thing you can do. Air that cold is already inherently dry (dewpoint is so low at that temp that it just can't hold much moisture). The problem then becomes the moisture you add to the air by breathing, combined with very cold windows. You'll see people driving down the road with frost on the inside of their windscreen and you know it's because they haven't figured out to take it off "recirc" when it's that cold. Around here, we only use the recirc mode for really hot days to feed the air conditioner with air that's cooler and already dehumidified from inside the cabin. Clearly a moot point with a convertible.