What is the reason Micro Cooling Fan noises are

1, making the blades issued a "buzzing" sound when rotating, "Micro Cooling Fan" motor bearings loose.
2, causing the fan blades are stuck or grazing, the fan motor bearings nipple axial deviation occurs, issued a "chug" sound.
3, due to the gasket wear, "Micro Cooling Fan" axial movement of the motor, the axial gap increases, issued a "chug" sound after power.
4, "Micro Cooling Fan" easily into the fan bearings with dust condensation together when the ambient temperature is low, the fan motor bearings are used in low-grade oil, increasing the resistance to rotation of the motor, the motor issued a "buzzing" sound.