It is going to damage the starting winding of the coil thus the entire coil. In addition to this, in my view, No problem. There should the voltage rating is equal or more than original capacitor. Fan will work. but it is unnecessary, and costly. Finally, capacitance is inversely proportional to voltages .
C=Q/V
where C is capacitance
Q is charges
V is applied voltages
if we are interested to increases the capacitance than. According to above relationship voltages will reduce and as we know a capacitor is charge. if we are using capacitor of higher rating, then a capacitor is capable of storing a huge amount of charges.
