Dashboard light

Hi guys just a quick one when I turn on ignition all the panels on instrument panel light as they should eg miles temp and the big bottom bar that displays faults all backlit green.
However when I turn lights on the big bottom bar illumination goes out.
Has anyone had this problem. ?
Is it common fault ?
Or am I just searching for a bad earth somewhere from front to back on the lighting system.

Normal.....nothing to worry about!! Supposed to do that!

When you select a trip computer reading the backlight will return!

Brill that's another tick and I didn't have to do anything .... Cheers Ant