I been looking for some used illuminated tread/sill plates for my 2011 XJL and found a couple. The left rear one illuminates but the front right one doesn't. They look virtually brand new, so I would think they weren't in service very long. Power is getting to the non-functioning unit because the black "electrical disk" on the underside gets rather hot after a short period. Is there any part or component that can be replaced/switched out without having to buy another(expensive) unit? Any help/advice would be greatly appreciated.