High-Level brake light failure!

Can't help you with the wiring lay-out but you do know that the 3rd brake light DOESN'T have to work to pass an mot...

Not at all, I've got a rear spoiler on my Astra with a 3rd brake light that has never worked since I've fitted it. Had it in for at least 4 mots at different places and nothing has been said by any of them. The only ones that have to work are the ones in the rear clusters. Same goes for front fogs, I had another Astra where I changed the front bumper that had fogs in but I never wired them up. No problems with that either. They are an optional extra afterall.

Fair enough... Odd how at least 4 different MOT stations never mentioned or failed it.

Agreed though, I'd rather have it working too!

doe sthe rear wiper work by chance and the boot lock??

i had same issue and was changed under warranty
to replace mean remove whole spoiler

as a note:
i asked asked about high level brake light as didn't want to get caught by boys in blue and was told that nothing to worry as long as two main ones light up and it is not part of mot and that was a seat stealer.

You have to take the Boot lid surround off and then there is 3 bolts to remove the spoiler.

Unplug the light from the wiring loom and remove the spoiler from the car. Looking into the spoiler you'll see to holes with screws at the bottom, undo these and the light will fall out of the spoiler.

The light unit is sealed and is a common problem to die, you have to buy a new unit from SEAT, it was about £56 inc VAT when I did mine last year.

Oh and I have never seen an MOT failed from a faulty 3rd Brake light as long as the 2 main lights are working correctly.

When you remove the boot lid plastics the plug is tucked into the boot lid itself (top centre), the wire then runs through the lid via a rubber grommet.

No worries mate. It's not a hard job to do, it's just a ball ache of one!
Plus the stealer stings you too

I'd say that if it doesnt work its a fail!

http://www.motuk.co.uk/manual_130.htm