Sat Nav draining Battery

[PJutla]

Hi All

Newbie here

Been trying to help my brother sort out a battery drain on his 2006 X5 (im in the UK, so i dont really know if theres any difference)

The battery is being drained over a few days by the Sat Nav drive. He used to pull fuse #75 when he was not using the sat nav but has since pulled out the cable from the back of the sat nav drive itself. This has stopped the battery from being drained.

It seemed as though the drive kept the navigation and audio system on. If you looked the screen, instead of the screen being grey in colour as it is when it is off, it appeared black - like it is just before showing any image.

Anyone know what could be causing the system to stay running and drain the battery?

Thanks for any help
Prit Jutla