Foggy windows

Hi everyone,

So this time of the year is foggy windows back again.
Did a search on this subject but looks like I covered most common issues so far:
AC works spot on, changed some seals couple of days ago, did a refill and leak test and it's fine.
Pollen filter is nice and clean and dry
I can't find any moisture on the carpets or any other part of the interior.
For the last couple of days the car is parked in an underground parking lot so it's safe from negative temperatures overnight, but after I drive for a couple of minutes in the morning with the AC on it still starting to mist slightly and it really bugs me.
Prior to having the AC system checked I suspected that was the issue as there were only about 250g of refrigerant left in it so I had high expectations after I sorted it but looks like it's another hidden issue 😔
Any ideas?
P.S: my other vehicle that is parked in the exact same spot overnight doesn't mist one bit, even if I sometimes forget to turn the AC on.

Hi, same issue one year later. Only this time it's even worse- I found the inside of the windscreen completely frozen. The AC works but even after 30 mins of driving the windows are barely de-fogged. Pollen filter is ok. Driver's carpet (it's an LHD car) is only slightly moist, not sure yet if that's caused by some clogged drain, will check it. What I find strange is that judging by how much moisture thre's inside the car I would've expect to find literally a puddle on the floor but there isn't one.
Any ideas before I start do dissassemble the whole god damn car?

Usually indicates you have a bit of internal water somewhere doesn’t it? Find the leak or get a big dehumidifer in it for a day or two and then get some small dehumidifiers on it to minimise the internal fog.

ripp said:

Hi, same issue one year later. Only this time it's even worse- I found the inside of the windscreen completely frozen. The AC works but even after 30 mins of driving the windows are barely de-fogged. Pollen filter is ok. Driver's carpet (it's an LHD car) is only slightly moist, not sure yet if that's caused by some clogged drain, will check it. What I find strange is that judging by how much moisture thre's inside the car I would've expect to find literally a puddle on the floor but there isn't one.
Any ideas before I start do dissassemble the whole god damn car?

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Be surprised how little water it takes to make that look like a big problem on the glass. And, IIRC the a/c might not work if it's below ~3c for instance ? Could be wrong....

First place I'd start is the boot - is the wheel well / floor wet ? It might be the grommits as they always shrink/fail/get old.

the boot is bone dry, so not there. The AC works at every temparature, I have the car for 20 years now, has seen -20 celsius and worked fine in the past

Even when I have had both front foot well sponges absolutely sopping wet with leaks - the A/C usually demists the car within a couple of minutes.

Only had a thin film of ice in the front windscreen twice this year too. The last was when it was -9 overnight.

Ive used some anti fog sh#te from rainx i think it is in the past, put on two coats and it does work, seems to last ages so you dont need to put it on much

In my 2012 Kangoo I had the scuttle blocked and water ingress in through the bulkhead and the AC always managed to sort out any misting. It sounds like you've done the things I would have suggested but maybe get a dehumidifier in and see what it collects.

VenomUK said:

In my 2012 Kangoo I had the scuttle blocked and water ingress in through the bulkhead and the AC always managed to sort out any misting. It sounds like you've done the things I would have suggested but maybe get a dehumidifier in and see what it collects.

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there is one more thing I found out about recently but never heard of the clio comunity discuss about: it's something that's called AC dryer filter or some sort- it looks like a tiny bulb on the AC piping under the hood. Some guy said he replaced that filter on his bmw and it cured the problem. Here's a picture of it:

it's located on the left side when you open the bonnet, near the top of the fender - part number for it is 6000073794
So I begin to wonder if that could be it, given the fact that there is little to no moisture visible in the car and the AC does actually work (coolant level is fine and it clicks when you turn on the AC)

But even if something in the AC is system is at fault, it still does not explain why I leave the car perfectly dry and the next day I find the windscreen completely frozen on the inside- so theoretically there has to be some stagnant humidity inside the car somewhere. I'm confused to say the least

Darren S said:

Even when I have had both front foot well sponges absolutely sopping wet with leaks - the A/C usually demists the car within a couple of minutes.

Only had a thin film of ice in the front windscreen twice this year too. The last was when it was -9 overnight.

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Exactly- this is why it confuses me- as it looks like the AC system should take care of the issue but it doesn't. But I'm about to dive into it these days and will come back with the results

I never knew about the filter. I’ve often thought about AC systems and are there serviceable items in the complete system. I heard once and not sure if it’s rubbish but the dryer needs replacing as it collects water? Not sure if that’s true or something in the system collect water and over time needs replacing to keep the system optimised?

Perhaps some AC experts on here may shed some light on this

VenomUK said:

I never knew about the filter. I’ve often thought about AC systems and are there serviceable items in the complete system. I heard once and not sure if it’s rubbish but the dryer needs replacing as it collects water? Not sure if that’s true or something in the system collect water and over time needs replacing to keep the system optimised?

Perhaps some AC experts on here may shed some light on this

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That would be interesting to know - especially as these systems now are 20+ years old.

It might be worth checking the recirculation flap thing in the drivers footwell. Mine sometimes gets stuck so isn't getting the fresh air in which causes my windscreen to get loads more moisture on it.

realnumber 1 said:

It might be worth checking the recirculation flap thing in the drivers footwell. Mine sometimes gets stuck so isn't getting the fresh air in which causes my windscreen to get loads more moisture on it.

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boys and girls that was it
Although I accessed the flap by removing the scuttle panel- it is located near the fan but further back, but easy to reach by hand. Mine was almost closed and thus blocked to the recirc position. I started the car, turned on the climate and pressed the recirc button on and off to see how it worked- it barely moved, not fully closing or fully opened either, so something's broken there, but for now I pushed it by hand to fully open to allow fresh air, wend for a drive and voila- clear windows!
When spring comes I'll take it apart once more to figure how I can fix it, because it's nice to have the recirc function when needed (especially in the summer when you can cool the car more efficient)
Now I remember that in the summer when leaving the climate on auto, it often went by itself into recirculation, but it still struggled to chill fast, when extremely hot outside even after 20 mins the fan still blew quite fast, only after longer trips the fan speed settled- clearly if that flap is miss-behaving for some years the climate is nowhere near as efficient as it should.
But for now I'll leave it like that, it's too cold to work on the car
I read thatyou can reach the same flap from the footwell as you say, I haven't tried it yet though.

That's handy to know for future reference going forward. think its a lesion for all vehicles suffering the same issue?

Glad you got it sorted. To cover off an earlier question, the drier component in the system is to dry the actual refrigerant loop and remove moisture in it for efficiency. A properly serviced and gassed system would be vacuumed down first before it's filled to remove any moisture laden air anyway but the drier is there to capture anything left over as you're never going to pull a perfect vacuum within the system before filling.

It's not impossible that it could become saturated and no longer able to absorb moisture and you start getting degradation of the system performance (especially if you've had a very small leak long term and kept refilling the system yourself without getting it fully vac'd down and refilled professionally), but it's not the first thing I'd jump to checking.