oven fan is not working why?

It may be defective - seized bearings (possibly) -jammed up blade (perhaps) - open circuit motor winding - wire fallen off - no power arriving at fan for some other reason.

You do not mention the make & model of your oven.

This is not a very sensible answer - sorry - an appliance engineer may be able to diagnose the problem and resolve it.

In the meantime you will just have to cook without the fan.

Good luck...

Peccavi
June 2010