Understanding Tiny Cooling Fan dead

Those factors fan dead? The so-called "Tiny Cooling Fan" means the fan is dead can not be started in accordance with the provisions under certain angles voltage situations. Test method is to adjust the fan before each pole in turn placed the Hall IC, and then slowly increase the voltage until the start, if the poles in less than a predetermined voltage value before the start, on behalf of qualified, if the level of difference, start voltage exceeds the provisions called dead.
Influence "Tiny Cooling Fan" factor starting voltage are:
1. Rubber magnet poles magnetized uneven.
2.HALL IC sensor sensitivity bad.
3. "Tiny Cooling Fan" rubber magnets magnetized magnetic field is too weak.