Euro Truck Simulator 2

Euro Truck Simulator 2

SiSL's Mega Pack
How do I turn on ambiant lights and the illuminated accessories in the cab?
Hey, as the title says, I can't manage to turn those said lights on.

I've tried to go to the options and turn on "secondary vehicle lights" but it doesn't change anything.

Any idea? Maybe I should download the customisation mod?

Thanks in advance