86 suburu gl door locks

Ok customer comes in with no door locks every time he puts the fuse in for door locks it blows imediately. So I know there is a short somewhere but I have to find it. I need info on this car like wire colors,location if possible. I checked the fuse panel and the fuse for door locks has continuity to ground on both tabs with the fuse removed . THe customer told me he had a radio put in and then the locks did not work, but he does not want to go back to that shop because they do not know what they are doing. Any ideas i was thinking maybe when they put his speakers in they drilled through a door lock wire which may be grounding it out(blowing fuse evry time) Any ideas??

that sounds like a good place to start but i would also check inside the door opening boot on a vehicle that old the wires inside there usually crack and short out in there