There is an auto setting, at least on the 7 inch system. When in this mode the screen brightness is linked to the headlight switch, so dims when the lights are on. If you have the auto lights feature and this is switched on, then the display will follow the headlights on/off. Its adjusted under the System Settings > Display Mode > Day/Night/Auto.
Im aware of the autofeature, but it doesnt seem to work on my navi. If i put the Auto on, there is no change if i set the headlamps on, the screen seem to blink a bit, but there is no change in contrast/brightness. Maybe there is some hidden features that has to be used to enable that.
No tricks, as far as I know. Maybe in Scandinavia they have daylight running lamps configured? I guess if so then maybe the screen is permanently dimmed while the ignition is on. Doesthe brighnesschange when using the day and night settingswhen justthe nav unit itself is powered up? If not, I guess there is some kind of fault. Mine works 'as advertised'.
After reading a bit in the Norwegian Mondeo club forum about the Navi unit, i got to know that the brightness of the navi unit is connected to that little wheel that controls the brightness in the dashboard also. That means that i quickly can change the brightness between night and daytime, even though the autofeature doesnt work.