Misting when parked after air-con used?

[edderby]

If I use my aircon (which I do at least once a fortnight, to keep the fluid going round) I often find that when I walk back to the car afterwards, the windscreen has condensation on the inside. This is (obviously) more pronounced in cold and/or damp weather, when the dew temperature is lower. I don't know why this happens, but I have a suspicion that the aircon drain might be blocked. I have owned the the car for 7 years and I have never seen any drops of water on the ground where it has been parked. Many cars seem to drip water slightly when parked after being driven with aircon on, so that's why I'm wondering if my Z4 has an aircon drain hole and it's blocked. Can anyone tell me where the drain is? Pictures would help!

Just for clarification, I realise that car windows often get misted up when left parked on a wet day, but mine gets much more misted up if the aircon has been on. The aircon itself works really well and demists / cools very effectively as I have had it regassed etc at the BMW dealer every couple of years. My car is a 2004 3.0i.

I would be interested to find out if there is a solution (or even an explanation) to this, but am not in a great hurry - having lived with the issue for 7 years so far!

 

[edd_jedi]

Condensation in the car almost always means there is water inside. Air conditioning by its nature removes the moisture from air, so that will not be responsible for your condensation. I'd check the carpets to see if there are any wet patches, maybe you have a leak.

But you are right that water should drop form underneath the car after air con has been on. It's roughly in the middle of the car.

 

[mmm-five]

Do you leave the aircon on all the time, or turn it on & off as required?

If I leave mine on all year round then I don't get anything, but if it's been in for a service the dealer turns it (& auto-lights) off and I end up with a bit of condensation after a day or two if I don't remember to turn it back on.

 

[Maniac]

As Edd says, its probably water in the car.. and you don't need much. My car windows are easily misted up in this weather with just water from my shoes etc on the mats. So, don't just rely on air con to remove water, run the interior heater on full blast to dry out the car whenever you can. I have both air con and heaters on in this weather to keep the interior dry and smell free.

 

[Bing]

I have the aircon / climate control on all year round, except sometimes when I have the roof down in summer and it seems pointless. I have read on here and elsewhere that you shouldn't switch it off for long periods of time as the system can get mouldy from damp accumulating in there. Yours is being serviced and filters changed I guess so you won't have mould, but it could still be getting / staying damp.

 

[edderby]

Thanks for your posts, yes I agree that condensation on the inside of the windows will be due to water in the car. The thing is though, I get a lot more of it if the aircon has been on and rarely any if the aircon has not been on. Also the condensation is on the windscreen only, not on the side windows. The condensation always starts to develop from the bottom of the windscreen, in the vicinity of the demisting vents. All the carpet is dry including under and behind the seats and under the mats. The battery well in the boot is dry and I regularly "rod-out" the soft-top well drain holes (to protect the roof motor from flooding) so they are dry too. I'm thinking that the dampness might be permeating up from the vents, from the aircon unit itself. Aircon dries the air out - on most cars you get a patch of clean water underneath after parking on a hot day - this is the water vapour removed from the cabin air, condensed in the aircon then allowed to drip away. My car never has such an emission of clean water - this leads me to think that the aircon drain pipe for the condensed water is somehow blocked and hence that's why I would like to know if there is such a pipe and where it is, so that I can check.

I don't leave the aircon on all year round like Bing does, but I do use it frequently, at least 20 minutes every 2 weeks, so that the internal seals stay lubricated. There is no mould smell in the car and the air from the vents is fresh, not musty.

Like I wrote, it's not a critical issue - it just niggles me. Something's a bit wrong somewhere, just not sure what and not sure where!