I have a fault on my 307 1.4 hdi in that the horn does not work. I have checked the fuse and checked the horn itself across a battery. Both OK. According to the Haynes manual there is a relay supposedly in the main fuse box (the one in the engine bay) but with the cover off I cannot see it. There are the fuses and the connectors but nothing else on the top surface. Does the top of the fuse box itself come off and they are mounted underneath I wonder. I still have to take the airbag off so that I can check the horn push contacts but would rather leave that if I can and find the relay duff?