The player definitely knows it's in the car. I can vary the dimmer setting up and down and the value changes accordingly, but the actual brightness of the display doesn't change at all. I know the car install is ok 'cos my spare Rio works fine. I can also force DC mode with Hijack and I get the same symptoms so I'm 100% sure it's got to be a problem with the player itself. I'll contact support as Tony suggests as soon as I get a moment.