Fan noise and footwell water - possibly related, methinks?
 

About a week ago, my S8 developed a noise behind the dash, reminiscence of an old hairdryer on a "low" setting. The noise starts about ten seconds after starting the engine, and isn't affected by engine revs, or by the fan speed of the aircon blower. Heater still works, possibly a little less effectively, but I might be imagining that…Ideas and suggestions welcome: from memory I had the blower motor replaced about three/four years ago, can't recall if that was the same noise though :( - it's age finally catching up with me …..

On a possibly related point, the car decided to dump a mug full of water on the passenger carpet today on a right-hand bend, and there's a definite sloshing sound - but only, I think, when the aircon is on - and the foam under the carpet is wet, though not sodden. The drains were cleared last spring, including the orange nipple thingy being flushed with a compressor, so I'm wondering if it's just the ridiculous amount of rain, blocked drains again, or related to the fan noise?

All ideas and suggestions welcome, as ever.

The noise could well be the auxiliary water pump. :(
Easy way to find out is to just press the "Rest" button when you get in the car and see if the noise starts.

I had to disconnect mine on both PF and FL S8's as they got intolerably noisy. PF is easy as it's an obvious plug, FL I had to cut a wire though there "may" be a plug somewhere to disconnect it.

Your water issue, i'd be checking the orange drains behind the tunnel covers and passenger side first takes 10 mins to take off, overmat (if you have one), carpet out, one screw in the tunnel cover, seat back and up as far as it'll go, might have to take the MDF panel off the relay board but you'll probably have to do that to dry it out anyway as it get's mouldy and stinks, panel moves down and forward slightly pull it away from the bottom. You can remove the orange rubber completely from the trans tunnel for cleaning.

I sometimes get a sort of fan noise, usually after a longish journey though, which is the sound of the sat Nav CD whirring around at an impressive speed

Water will be drains, need to clear all three sets, good luck!

This comment very much suggests the auxiliary pump, which you can easily do without.

Ta v. much for the advice - lots of water (> than 2 gallons) cleared out of plenum chamber this morning. This has stopped the noise from the pump (!) but not the water egress into the footwells. Aircon drains next...:)