Got a strange one here.

Old headunit (Sony died - usb plug faulty) so ordered new one and checked wiring as last owner did a hack job. Used old plug and b40 L200 audio pinout. Tried old head unit back in and turned on/off with key, radio now better and illumination worked. 10min later just after plugged in iPhone as it was intermittent on issue it died totally

Power wires were correct, speakers were all over place so sorted them. Lastly illumination and radio amp wires were not connected at all so connected them. As above tested and all good.

Yesterday I double checked wiring and constant, switched and earth continuity all checked out fine on volt meter.

Plugged in new head unit and getting nothing. Checked both fuses one under steering other in engine bay and they are fine. Checked volt meter and switched live seems fine but constant is awol, checked back to wire on original loom and nothing. Again fuses are fine.

So now at a loss where to look. Do I just assume wire broken somewhere and find another place to take a feed? Does the smaller plug that was for the compass/info display have a live I can tap in to? Any other thought or ideas?

Many thanks

John