I recently got my car fixed at a mercedes benz dealership. To repair the car they had to order a new fuse box and a transmission control module. After they fixed the car, I asked that they return the old parts to me. When I went to pick the car up, they returned the old fuse box but they kept the old transmission control module. They said they have to keep that part because it's a "core part". My question is are they allowed to do that? I'm thinking just because it's their "policy" to keep the part, doesn't mean it's legal for them to do that. My plan was to resell the old part. I'm thinking about suing them for the value of the part. It has to have some value, otherwise why would they have kept it for themselves?