Weird Whining noise - slow speed

[Mr K]

I have a weird whining noise when slow speed manovering. I have removed the missus but it still remains.

I initially thought it was the gearbox as it seemed go up and down with revs, only occur in 1st/2nd gear, and only in drive.

Whilst on holiday (and riding around in the passenger seat a bit) i found that pressing the ECON button it stops. It is audiable thought all gears and speeds but more so and low speeds (possibly due to less wind noise, possible because its louder, hard to say) but the pitch changes with the revs and gear changes.

Any ideas? some kind of fan on its way out? Im certainly glad its not the gearbox whining!

[Conan_the_Librarian]

The fact that it goes when you press the Econ button points towards the fan. However, you say it changes with speed in 1st / 2nd.

The Econ button does 2 things. Switches off the AC fan when it is running and de-clutches the AC compressor. The AC fab will only run when the temp of the LP circuit is high. Slow speed/stopped in traffic at high speed the air through the radiator is enough.

The AC compressor will run when you have the engine running unless there is low gas pressure or you press Econ. My suggestion is that the AC clutch may be to blame.

Open the bonnet get a mate to start the engine and rev it while switching Econ on and off. see if you can tell which it is. +++

[The_Laird]

It's the aircon - almost certainly. I've had the same with the A8 and S8. Get it regassed and it will go away (mostly), depending on how bad it is

[Mr K]

Having had a good listen its definitely coming from the aircon pump.

Will an aircon pump whine then when its low on gas or is it the bearings? A regas would be a nice easy fix!

[PsYcHe]

The aircon gas has a lubricant through it that keeps the pump going, so if it's low, then the pump won't get libricated properly.

For the sake of 30 quid or so, I'd chance the re-gas first.