It's been a while since I've been on this forum. Surprising how things have changed!

Last September we picked up our new 500 1.2 Lounge. On the drive home I noticed a kind of "shhhh" noise that lasted for a few seconds and reoccurred every few minutes. I hoped it would go away and over the Winter it did seem better.

However now the noise is back so I took it to the dealer last week. On a test drive I reproduced it and the mechanic said it was something to do with the aircon. He claimed some cars make this noise while others don't but it was nothing to worry about. They could replace the noisy part but it may be no better. I have tried switching the aircon off and the noise does go away. It is a noise that I can live with but I don't think it should be there.

Does anyone else's car make this noise? Should I get the dealer to replace the noisy part anyway?

Yep, ours does that as well when the aircon is switched on - always has done as far as I can remember.

Agree it can be a bit annoying at times but essentially it's just the air conditioning unit doing its job (albeit in quite a noisy fashion). Think its to do with the disposal of condensation that builds up as the unit is working (this is often something that is mistaken for something more serious when people park up and notice a leak under the engine after having used their aircon).

Not sure if many others have suffered from this though.

Oh yeah - if you're taking the car in anyway and they are happy to fit another part for free then you may as well let them get on with it; might make a difference.

It's the expansion valve, the liquified gas is being 'evaporated' in order to provide the cooling effect. A gentle hissing sound when this occurs is pretty much a normal thing.