See "220V Cooling Fan" operation and power-speed performance will rotate back and forth several times, shaking his head switch, check whether the failure or assembly too tight, in the process, the fan mechanical transmission parts should not abnormal noise. Fans in high, medium and low speed, "220V Cooling Fan" motor and blades should be smooth, low vibration, low noise. Fan shook his head, shut down should be agile, non-stop, arrest and jitter, the speed difference of each block should be obvious, air angle bigger the better. When "220V Cooling Fan" stops, the shaft axial clearance is not more than 0.5 cm, the gap is too big, it will cause axial movement and there is a crash during the operation.