What is the pulley below the alternator?

[Rick448]

I was just checking out the engine on my 850 T5 and noticed a clicking sound, after a while looking around i found it to be the pulley below the alternator stopping and starting. What is this for? It appears to have some sort of mechanism which allows it to run freely, and then take up drive, hence making a small clicking sound. Is it PAS pump or something?

[fireclown]

think thats your aircon compresser. has yours got climate control. it should click in and out as it adjust temp ect.

[Rick448]

Yes i think that is what it is. It does have climate control yes. It's the first chance i've had to have a proper look under the bonnet. Cheers.