If your lights are not working, there may be several different reasons: 1- Check that the dynamo is correctly positioned against the wheel rim. 2- Check that the dynamo is properly connected. 3- Check the electrical connections (bearing in mind that if one light doesn't work, both will be short circuited)   Check the images below to learn how to perform these checks. If that doesn't work, don't hesitate to ask the technicians at your local Decathlon Workshop for advice, or contact us below for help.