Solar sunroof intermittent now not working

[HPsauce]

My question is, where do I start on diagnosing and fixing it?
The ventilation fan works totally normally except the solar sunroof no longer activates it.
For quite a while it had been intermittent, sometimes working, sometimes not, suggesting an relay or loose wiring issue.

I know there's a lot of stuff on the A8parts forum that could/would guide me but it's never up these days!
Where's a good place to start, checking voltages etc.? Or even just swapping a relay?

[Fredde9912]

Here are some current flow diagrams assuming you have a multimeter it's just a case of tracing where the power stops flowing.

[Fredde9912]

Here are some current flow diagrams assuming you have a multimeter it's just a case of tracing where the power stops flowing.

I tried to attach the images but didn't work will try to send you a message.

[Edit]
Same issue when trying to upload the diagrams but maybe you can find them yourself on Elsa if you have access.

[HPsauce]

Thanks. Yes, I think I have Elsa somewhere, and I have the old Bentley manuals as well; I'll need to boot up a virtual XP system to get into them though!
Just thought someone might say - commonest problem is X, start here.

[HPsauce]

I know there's a lot of stuff on the A8parts forum that could/would guide me but it's never up these days!

PROGRESS! The A8parts forum is up (how long though?) so I dived in, found the relevant threads (including the one where IT did a full retrofit) and have downloaded the entire content of them, text and relevant images, to my PC.
Now I know which relay, where it is, the wiring layout, etc. So I'll be diving in when the weather is a bit cooler and the cabin isn't 50C or more (due to no solar fan... )
Incidentally I did raise this very question there (A8parts) a while back (2 years ago) when the problem was just intermittent and Sean pointed me in the right direction. But I never got round to it and forgot what he said then ....
FYI: The relay part number is 8A0951253A and is stamped with the number 203. It sits in position 7 in the relay plate in the passenger footwell.

Of course, Sod's law says I don't have a spare 203, though oddly I do have a couple of 204's! Ordered a used one off eBay.
I presume the 204s are from taking out the starter relay when I had F125 problems and put a bypass wire in there instead. It's probably still there, I don't recall bothering to replace it. Maybe I never will? Edit: I must have done, it only starts in P or N.