The fan clutch can cause overheating. Basically it will be turning, but slipping to the point where it is not turning fast enough to draw the correct amount of air across the radiator and condenser. when engine exceeds a threshold temp (temp sensor/threshold is designed into the clutch), the fan speed should increase. Access to an optical tachometer should show the fan at the same speed as the pully driving it when engine begins to overheat. If it is slower, then the clutch is bad.

good info can be found here:
Diagnose Cooling Fan Clutch