I've got the same fusebox layout as Mick and Fuse 39 does Climate control,Radio, Navigator, Services +30(unswitched live), volumetric sensor, EOBD socket, cell phone, drivers door control and boot control!!! It's only 15 amps!!. It would seem odd that the Satnav part has reverse polarity protection and the radio doesn't? You'd think they both work off of the same internal power supply? I can't find any pictures of the back of the connect unit so still don't know if it's got seperate fuses? Maybe it is a radio code thing?