Windscreen fogging up

Skilid

Skilid

Skilid

Soldato
Joined
20 Sep 2006
Posts
2,828
Location
Hampshire
Hey people,

On the last 2 cars I've owned I've noticed that if I have the air con on, then switch off the car, then come back to it later and switch it back on, the windscreen fogs up until I turn the AC back on again. I know the AC works as a dehumidifier, but isn't it supposed to dump all the moisture? It seems to almost hold it in the system.

I got a good deal on an anti bacterial treatment and re-gas, which it is having done on Saturday. That is because it didn't blow that cold in the summer though and probably won't be of any help.

Ta.
 
Check your AC drain isn't blocked, it should dump water outside the car. Mine still did this despite the drain being clear though and it's quite common from searching around. Solution is to turn the AC off a minute or two before you arrive, works better if you open the window a little too. If I do that it never fogs up.
 
Possibly a water leak in the car, rear lamp maybe? So the AC is drying it enough to keep clear and when off the humidity climbs due to the water in the car.

Pollen filter been changed recently?
 
paradigm said:
You turn your AC off? :confused:
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I have manual AC and only use it in hot weather or when it's raining, to keep the widescreen clear. Or if it's stuffy in the cabin.
The compressor's too noisy for my liking and having cool air from outside flowing through the cabin is usually enough for me.

As for CC, never turn it off!
 
Im getting this too at the minute.

In the past its been due to the flap that recirculates their air getting stuck but now ive no idea and i CBA with getting under the car!
 
Jonnycoupe said:
To save fuel?

Why else would you get a 2.0 TDi Audi?
Click to expand...

I don't need to turn the AC off to get a decent amount of fuel economy out of it, I certainly don't see the need to be more uncomfortable in the cabin than I otherwise would be, to perhaps eek a bit closer to 70MPG on a run?
 
paradigm said:
You turn your AC off? :confused:
Click to expand...

Yes, because as said above the compressor makes a bit of noise and it also raises the idle revs, annoying if I'm sat in traffic and don't need the AC. It also resolved my issue which was identical to the OP's. I had all the carpets up and the dashboard out to try and find a water leak, there's no trace of one, so it's purely down to the AC not completely drying without being turned off. It drains outside perfectly fine (well, did until I broke the little drain pipe last week, but that was obvious because after a run the whole front passenger carpet was wet through, so it certainly wasn't leaking before that). I replaced the heater matrix due to a different issue, where it would fog up if the heater was on hot, but that was entirely unrelated and corresponded with a drop in coolant.
Even on a hot day, pressing the AC button a minute or two before I arrive at my destination and tapping the window down button to crack it open slightly isn't an inconvenience, and doesn't make me uncomfortably hot as the cabin stays cool. It eliminates the problem completely and leaves me with a completely clear windscreen when I start the car again without having to put the AC on again to clear it.
 
Jonnycoupe said:
To save fuel?

Why else would you get a 2.0 TDi Audi?
Click to expand...

LMAO

burn.jpg


Yeah I turn my A/C off when I don't need it. Just common practise really.
 
Indeed, the only noise you should hear is that of the condenser fan coming on. It shouldn't raise the idle revs by any significant amount either; the ECU should compensate for the extra drag but it shouldn't increase in RPM.


I never, ever disable the AC on my climate control. And the compressor makes no noise, it blows ice cold, doesn't smell, and doesn't fog up when I get back in the car.
 
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Howard said:
Indeed, the only noise you should hear is that of the condenser fan coming on. It shouldn't raise the idle revs by any significant amount either; the ECU should compensate for the extra drag but it shouldn't increase in RPM.
Click to expand...

Perhaps I'm confusing compressor noise with the fan then, that's probably what I meant. Sorry!
The revs increase very slightly, and the car feels different at idle with AC on. It's enough to be annoying over prolonged periods, but not enough that people would look at the car revving its nuts off sat still, if that makes sense. Once moving, AC on or off makes no difference.
 
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