Sascha748i,

If you turn on the light override switch on the pilots overhead panel the cabin lights will be on. You can also hit the "L" on the keyboard.

This has been talked about on this forum as a problem since in the real plane the cabin light switch is located at the flight attendant station.
I'm not sure if this will be addressed when the next fix comes out. Turning on the light override switch puts all the lights to bright.

Lou