On Our 2005 Volvo S40I We were having an issue with the AC Clutch disengaging after the clutch heats up or once the engine speeds up past 1200 RPM. From factory these clutches are set with a low tolerance. So after these run for a while the Clutch material wears down and this causes excess air gap which causes the clutch the slip and disengage.
So Behind the Clutch face and the pulley these comes with a set of shims to spaced the clutch out for proper tolerance. By removing the Clutch face and removing the thicker shim (of the 2 shims) this closes the gap that is caused by wear over time, And enables the clutch to operate properly. This is a simple fix, That costs near to nothing. if You end up renting the AC Puller kit from Autozone or Oreillys Auto parts, then You will need to have (3) 5mm bolts to screw into the clutch face to pull the pressed portion away from the clutch pulley, to access the Shims. Once the shims are removed simply install the clutch face and tighten the main bolt down snug. We hope this is helpful and fixs your issue with the AC on Your car.