Steamy Windows

[s4avant]

The air con system in my car will clear condensation from the window glass fairly quickly but seems to hold onto the water vapour, only to dump it back into the car interior the next time the car is used.
The problem can be solved by not using the air con but relies on a bit of a wait while the engine warms up.
Is there a fault with the air con or am I doing something wrong?

[andy-xr]

You sure it's the a/c dumping it back in, or have you got a seal leaking somewhere that's causing damp?

[marshalla]

If you're sure that the aircon is retaining moisture then you may have a blocked drain.

Alternatively, you have a leak somewhere that is letting in moisture from the outside.

[ben5732]

Possible heater matrix leak?

[Dog Star]

Zero cost check: check that your pollen/cabin filter(s) aren't blocked.

[towser44]

Mine seems to steam up quite easily even when it's been dry for days and I've changed the pollen or cabin filter as it is called too. A mates Audi A4 does too, he reckons all the electrics in modern cars don't help, but I'm yet to be convinced!

[PlayersNo6]

Dog Star said:

Zero cost check: check that your pollen/cabin filter(s) aren't blocked.

+1 and check your foot-well carpets for dampness - may be a blocked drain hole somewhere.

[Sheepshanks]

I try and dry my Merc out by turning the a/c off before getting home, but on many cars these days with variable compressors, it doesn't shut off completely for about 15-20 mins. I imagine Audi is the same - you can tell this if you turn the a/c off on a wet day and the windows stay clear for a bit, then suddenly mist up.

Having said that, even my wife's Honda Jazz, with a clutch driven compressor, pretty well needs the a/c on all the time to keep the windows clear.

Inevitably this means you're leaving the car with the evaporator wet - start it up without the a/c on and that moisture is dumped into the car.

[LouD86]

Right OK, simple one, I see it a lot in the trade. Make sure your ventilation is set to fresh air, not recirc.

Otherwise, all you are doing is recirculating the moisture. And if you have AC, switch it on. Don't go on/off/on/off, just leave it on, it will keep it clear, aslong as you have no leaks!