Noise when aircon OFF

[jyates]

I have a xk8 x100 that has developed a noise when the aircon is switched off, if i put the aircon ON noise goes away. Also when i kick it down and push it a bit the same noise appears. With the bonnet up it sounds like it is coming from the front of the engine. Any suggestions would be great fully received Thanks

[Astromorg]

Surely that must be the A/C compressor clutch that's rattling when not magnetically held solid while on load. Maybe its worn or loose?
My understanding is that the clutch also disengages if Kick Down is used, hence the noise then.
Does the noise come and go in normal driving as the A/C compressor comes on and off load (as it should)? Of course if you're low on refrigerant, that normal on-off cycling may not occur.