If your fan runs slow, then in most cases the culprit will be the capacitor. The fan capacitor might be leaking or damaged due to its constant charging and discharging cycles.
How to replace your ceiling fan capacitor?
It is a pretty simple job, you don't need to call an electrician to change the fan capacitor. You can save some bucks by doing it yourself. Here is a step by step procedure
1. Know how a ceiling fan capacitor looks like
This is how it looks like, by the way it is an old one and there are other capacitors which comes in box shape also. Like this one
Irrespective of the shape, the capacitor does the same function.
2. Now to the real thing, open the housing of the ceiling fan ( the housing above the motor)
The white cylindrical thing is the fan capacitor, by the way this ceiling fan is a pretty old one never mind.
3. Now have a look at the capacitor specifications i.e the values on the capacitor and get a new one with the same specifications (i.e the same values, it is important). Fan capacitors doesn't cost much and you can get it from any electronic component shop. Fan capacitor usually costs around Rs.25
4. Now cut the wires going to the capacitor and solder or join it to the new one. Close the housing and you are done.
Note: The reading on the above capacitor is
2.25 MFD 5 % tolerance
440 VAC, 50 Hz
The new capacitor should have the same ratings as the older one.