so i've had my car a couple of days now, new reg on 1/9.

the aircon makes a low whirring noise every so often when its switched on (i only use it in auto). its not loud, but there is an obvious whirring coming from it now and again when its running at low speed (silence mostly then a light whirr/whine for a few secs, then silent again). goes away if i turn off the aircon.

is this normal?

 

In a word -Yes

 

Its just the compressor on the air-con engaging, its got an automatic clutch that runs off the drive belt at the front of the engine as needed.

Works similar to your fridge - i.e not continuous.

Edited to add: if you can hear the compressor you obviously havent got a loud enough exhaust