Ive just bought my 1st Mercedes, a 1996 C250 5Cyl.Diesel (I live in Scotland, UK. Diesels are quite common here).I have a problem with the electric sunroof. The back rear corner sits about 1/2 inch too low & when I try to operate it nothing happens except a kind of grinding sound. Does anyone know how to get into the mechanism ? Ive tried the manual handle but it seems to be jammed. HEEEELP ! ! !