If you open the casing of the fan (top casing) you will see a capacitor in it, something like this: http://image.made-in-china.com/2f0j00RBwtG...itor-CBB61-.jpg . Try to change this capacitor to a new one, and it will improve your fan speed. Remember to change the exactly same capacitive capacitor. You can get it from electronic store, price around RM5.