how to renew reversing light switch?

It is a simple task. My answer assumes you have no experience because you ask it on a website and I question your skill level.

Is the bulb blown?
Have you checked power to the bulb?
Is a fuse blown?

The reverse switch usually resembles a large bolt head with two wires leading from it. It will be on the gearbox housing. The grearbox should be on the passenger side (UK) of the end of the engine it should not be hard to find. You can then test the switch where it is. You should be able to remove it with a spanner or socket.

Jmmy
August 2008