UK-POLOS.NET - THE VW Polo Forum

i've noticed that the rear seat of the car feels damp (on the top fabric of the seat) and can't see where the water is coming in. any ideas?

Is it actually damp or just cold? Do your windows steam up excessively (which would indicate the presence of damp)?

Condensation on, or fogging up of, the interior surfaces of the glass is a natural indication of the state of saturation of the air (both inside and outside the car) when the air temperature (and therefore the temperature also of the cabin's solid structure, trim and upholstery) is below a certain level. Getting rid of the fogging is a matter thereafter of either raising the temperature of the cabin's solid structure itself or of the air in the cabin, the latter by which you'd make the air less saturated than before. This takes time to do.

Particularly where you're starting from a situation in which the car's been left out in the open, ungaraged, during a very cold night (or day), you've essentially got to wait for the heat generated by the engine, conducted through the heating system, to warm up sufficiently the cabin's air and also the windowglass. Only then will the inside of the windscreen and other windowglass clear. I don't see that turning on the AC is going to help much, as I'm not aware that AC quickly raises cabin temperature. It may nonetheless remove some of the saturated air - but surely more saturated air from outside would be sucked in?

One obvious, though flawed, bit of advice you sometimes hear from other drivers (and here I mean generally, not the more-sensible and informed people who use these forums) is to just get in the car and drive off, to more-quickly get the engine heated up and thence the windscreen, etc cleared. But of course, no right-minded driver would do that with the windows fogged up.

Do remember also that the cabin is not 100% sealed up when all the doors and boot are closed, no matter what the various doorseals are like. That's because there's an intentional through-cabin air passage - outside to inside, then inside to outside - always operating, air coming in via the pollen filter and exiting via an aperture that's hidden away between the outer and inner skins of the vehicle boot. Air recirculation mode speeds up the passage of this airstream. However, the latter is intended for removing stale smells, not simply cold, saturated air. So even turning on air recirculation mode won't help much, as the replacement air would be coming from outside.

Drying off the glass with a suitable rag or chamois pad stored in the centre console, should help the process a little.

Just a comment about the part AC plays in drying a car interior out, if the chiller is enabled, it will cause the evaporator in the air box to get quite cold and it is passing the wet cabin air over that cold evaporator that strips the moisture out of the cabin air and the condensate escapes out through a drain hole under the soundproofing in the engine side of the firewall.

On my Polo, I think the chiller/evaporator is situated further forward than that, in the frontal wing space on the nearside. As a result I've noticed the very occasional amount of water/dampness on the garage floor, right under that part, some hours after having returned from a long-ish journey during which I'll have had the AC on. But, thus far, I've never found it in cold weather, only when I've had the AC on in the summer. (I nonetheless agree that, if the chiller is up to the job, it should be able to do it in virtually any weather). I try to adopt your recommendation, RUM4MO, of turning off the AC about 5 mins before getting home or to a destination, and using air recirculation mode instead, but the mere fact of causing a water stain on the concrete drive or on the garage floor is actually neither here nor there to me.