"Waterproof Cooling Fan" at the beginning of the impeller operation and regular inspection of all time, as long as there is an opportunity, we must check whether the impeller cracks, wear, dust and other defects. Whenever possible, the impeller must be kept clean, and regularly use a wire brush to the top of the dust and rust leather, etc., because with longer run time "Waterproof Cooling Fan", the dust since it is impossible to uniformly attached the impeller, causing damage to the impeller balance, as well as causing the rotor vibration. As long as the impeller was repaired, it will need to further balancing. If the conditions, you can use the portable test instrument in the field balancing balance. Before making balancing, you must check whether all the retaining screws and tighten. Because "Waterproof Cooling Fan" impeller has been running for some time in the unbalanced state, these bolts may have loosened.