Watch around the middle of the motor gap, as long as "220V Cooling Fan" flexible rotor gap as small as possible. Check to remove the front fan grille, Hold the fan in the middle of the protruding portion, sliding several times. Hand slowly turning blades, blade rotation should be smooth relaxed, do not touch any part of the stop blade gradually diffuse natural stop. Watch the running track three blades from the side, if there is no obvious bias, then "220V Cooling Fan" relatively stable high-speed rotation. Fan stability is very important, in the most unfavorable position the fan into a 10°angle with the plane when the fan should not be overturned. Quality "220V Cooling Fan" should have the following characteristics: appearance, lines, color nice; plating smooth, shiny, no yellow, rust, peeling and waterlines phenomenon; film hard, smooth, no bubbles, scratches, no paint off, open at the end, hanging paint or paint mix different phenomena; decorative pieces without damage, front and rear grille fit tightly, no distortion, no solder wire nets loose sealing off and so on.