Please help!

Ive striped the car to the diversity unit and found there is no power to the unit itself (tail gate window, rear wiper, central locking,radio)
does anybody know where the wiring goes to for the diversity unit so I can start there
thank you in advance

 

My first thought is the wiring in the hinge area, which over time, and years of getting bent in the same place from opening and closing, begins to destroy the sheath and the strands within the wires.
I can't remember which hinge it is, but it should be easy to tell once you begin taking the wing and other things off.

 

See the post from Chesney72 in https://5series.net/forums/e61-touri...t-72751/page2/ as this explains how to get to the wiring, it's in the hinge and a common fault, a design flaw.

Pay attention the hinge spring as you remove the rear window as suggested.

There's a good chance you'll find the wiring by the hinge has been pinched frayed or even cut by the hinge. With luck you'll be able to splice the cable(s) back together, wrap them in a protective sleeve and replace rather than having to replace the whole loom.