Reverse Lights

[john p]

My reverse lights have never worked in the one year I have owned the car,took it to be serviced today and asked them to have a look.When I picked the car up they had fixed them by changing the fuse.I had not checked the fuses because everything else on the car works and according to the manual and bible they share a fuse with other things.When I got home the fuse had blown again and no reverse lights.There doesn't seem to be many wires going to that fuse terminal but it's a 20 amp fuse.Any ideas anybody?It's a 1993 Chim 430.Thanks.