trying to find the fuse for the central locking system,any body any idea

 

Year of the Fiesta will help? The very fact it has C/L though suggests it to be a modern MK 5/6/7 most likely?

If you lower the glovebox the fuses are behind there (Incidentally there will also be an engine fuse box), don't know which one but it's almost certainly going to be 10A (Red fuse). If you have a meter it only takes a few minutes to check every single one in situ!

Martin