Open door no radio/cd

Changed to a Sony cd player in a 300tdi.
Open the door or switch interior light on & radio/cd switches off.
Presume they share the same wiring loom?

Yes they share the same 20amp fuse along with the alarm, clock and trailer socket so if this issue is since you fitted the head unit i would go back to that and re-check your connections first.
Seems to me that there is a earth fault and poss at the head unit but you will have to check.

The fuse is No6 in the upper satellite fuse box. is your clock resetting every time you open a door?

Clock has always been dim & doesn't progress the time.
Will check trailer socket (charging system first ) as I only fitted theses recently.
If I put original radio in (radio works ok),but still no interior light working?