Whirring sound from centre dash
 

This is interesting, and I think its related to the climate control.

Turn on ignition and I get a whirring noise from the passenger side of the centre console, this noise is always present even when the climate control is completely turned off. The noise is quiet loud, and can clearly be heard with the engine off.

If I thump the side of the console the noise changes slightly before returning to how it was before. So its a motor thats running, but I have no idea.

If I turn on the climate and press the flap controls, they are all working and the air distribution is working correctly based on the buttons I press (both sides).

I wonder what that motor is? and what will stop working when it fails.

Just one of a number of minor issues to be fixed, the A8 is off to just outside Malaga again later this year but this time its being driven via the Eurotunnel / Calais all the way down which will be an additional 1.5K miles on last years trip.

I'd put money on it being the auxiliary hot water pump.
Mine did that (in the old car) and I disconnected it in the end - takes 10 seconds and no tools and minimal side effects (slightly slower to warm up the cabin on a cold day).

The way to check is to press the "Rest" button after having used the car and turned everything off and waited for everything to stop.
That will fire up that pump and make the noise again.

See: http://forum.a8parts.co.uk/showthread.php?t=4052

Are you sure its not the climate control module faulty as per IT's thread HERE?
Even if the flaps were working fine if the control module was faulty then it would make them operate when they shouldn't - and thus result in motor noises

Since the weather has been sunny and not too cold down here today, I set about identifying the cause.

I removed the passenger side trim from the console, what a pain that was. and had a good listen and its not any of the flap motors. Whilst in there I checked the orange drain and it was bone dry.

Listening very carefully, I have now identified the cause. Basically it is the climate control controller. There appears to be a fan inside thats making a noise, so I removed the screws and confirmed this.

Battled for a few minutes to put the side trim piece back on, and the relay box cover, then the carpets and now find myself in need of a replacement climate control controller.

So now on the lookout for a cheap 4D0 820 043Q

Had another look today, tried to remove the thing so I could take a look inside. Managed to get all the connectors off, except for the heated seat connections. Cannot for the life of me see how the connectors come off.

The sound is coming from (assuming in situ and RHD car, sitting in drivers seat) the rear of the unit on the UK passenger side. At one point all was quiet, until I realised the fan had stopped working. A gentle tap and the whirring sound was back, if its something I can sort it would save potentially a replacement cost.

Did you test that it's definitely not the auxiliary hot water pump?

Yes, the sound is definitely coming from inside the climate control module itself. I can get another for around £100, but given the age of these now, there is a risk that the same fault could be present or about to happen.

I would take a chance to open case to check the source of sound. Also, I think the problem is well documented since all Audi use about the same design on climate control manufactured by Hella. If it is ventilator noise I'm sure there is cost effective way to change the motor or bearing. There must be companies who will offer desoldering old thing and soldering new part.

Took the unit out of the car today and stripped it down, ended up with the main circuit board and the front controls. Took the dismantled unit to the car and plugged it back in, and have actually identified the cause of the sound.

Behind the front controls, dead centre at the top there is a little grill. I am not completely sure what the purpose is, but there is a little motor behind there driving a fan that is judging by the crap inside the unit around this fan, sucking air into the unit. I can only assume this is to pass air over a temperature sensor, to establish the interior temperature.

A vacuum and air duster blew out a large amount of dust, but despite this the whirring continues.

Its all put back together now, it still works so will just put up with it for now. You don't realy notice it with the engine running, the sound is only audible with the engine off and ignition in pos.2, even then you need good ears.

I would try to clean that motor first. It maybe good motor with just lots of dust around. Or I'm sure it's possible to find new motor and change only the motor.