Topic

One or two applications of a large hammer or a considerable number more from a small one.
Ah the non destructive bit didn’t register, use the small one.
M

Before concluding that you have problem with BCU and take actions on BCU I would first do the following:
- take out the relay from fusebox and make connectivity test from switch positive to corresponding relay terminal in order to be sure you are testing correct relay.
- test that incoming terminal on the correct relay have 12 V power applied
- if above test if succesful then I would bridge two corresponding relay terminals in the fusebox and by that confirming BCU ground signal to relay coil is realy in question here

If I am certain I have ground connection problem with BCU I woul definetly contact Paul from https://www.technozen-electronics.co.uk/ for all questions related to BCU.

That was very good advice. The negative from the BCU to the relay coil is ok as you suspected. It is the positive supply to the relay coil that is missing. I will remove the fuse box tonight and check for a broken wire or failed in line connector.

Sorted now.
It turned out to be Fuse 9 (in the passenger compartment fusebox). I cant imagine the passenger window will have caused the fuse to blow given it only runs the + side of the relay coil, not the motor itself, so not much that go wrong there.
The only other device that I can see runs off fuse 9 is the engine bay cooling fan so soon as the weather improves i will check the state of the motor and the wiring around it.

I’m sorry I can’t help, I’m away again & in part of our fair land where the internet is the gaps in fishing gear.
I really should download the circuit information onto my phone, however even with the relatively simplicity of the diagrams, fault finding on a 3x3 screen isn’t straightforward.
M