I'm a bit puzzled on how the AC compressor on my 2010 insignia works. I was under the impression that when the AC is off, the clutch in the middle of the compressor is free to rotate. And when AC is on, clutch engages and rotates with pulley. 

My compressor isn't engaging/ disengaging when i toggle my AC switch. I assumed that if AC pressure is low, compressor would not engage at all. However it does look like the clutch is always engaged. My initial thought was that the clutch has seize to the pulley, so i got under and tried to persuade some movement, with no joy.

Am I monging it? I have it in for a AC recharge Saturday, but I'd rather reschedule if i need to change my compressor clutch.

Compressor part number P13232307

TIA 

ive been having a similar issue on my Meriva, just got back from the garage and my compressor is naffed. 

im not sure if its applicable in your case but on mine there is a relay switch in a very well hidden fusebox located behind the dash accessed via the engine bay. not sure if yours is the same but its worth looking at.