From most "AC Fan" usage, the effect the fan will be affected by many factors, when you click on the fan speed can not reach the rated speed, be sure to check the bearings, if there has been damage to the bearing, the fan the impact is very big, this time, the need to replace the new bearing, otherwise the effect of the fan is not going to play out, if the internal bearing a lot of grease or dirt lot, to completely clear the bearing and grease added, with carefully check whether abnormal commutator surface or brush and commutator is consistent, if the commutator surface oxide layer should be sanded with fine sandpaper, if the commutator and brushes should be adjusted to coincide with the non-contact good condition, the final inspection of the rotor winding, short-circuit phenomenon, found that a short circuit is recommended rewinding.