I had an x920BT installed by a local shop with no apparent problems and the unit works fine except the screen does not dim at night.

I have the Day/Night Display set to Automatic but the screen never changes; it's always bright.

The installer says it's because the car's CAN doesn't use 12v power to the auto dim functions.

Suggestions welcome.

the installer is right,newer cars dont have a old fashion illum wire at the radio, the factory radio get its brightness commands from the vehicle's data bus line, however they should find another source for the illum wire to hook up to (this may cost a little extra)

basically you need to find a illum source, like a light bulb in the gear selector, or in the ashtray, and tap into that, with a lot of cars this may be tricky to find a source that is easy to get too

I had the same problem. I tapped into a parking light circut at the fuse box. Works great