What do you mean by 'unit'? The whole headlight? Or "the metal box about the size of a pack of cards attached to the side of the headlamp unit"?

If the latter, there must be a connection somewhere. I'll have a look on the spare headlight before I start!

The metal box :) It may have a connection at the box itself, or may be fed from connections inside the headlight unit.

There's no way that's coming off with the headlight in place, so it'll have to wait for the weekend!

Still don't really understand what the issue is as the replacement bulb (not new and a lower 'rating') is behaving much better (but not 100%). David's poor connection to the bulb problem makes me wonder if this isn't a similar issue.

Still, headlight out on Saturday.

Could be a tired component in the ballast if a lower rating bulb is happier.

Going to try to swap the ballast at the weekend, but mine don't look like this:

http://www.ebay.co.uk/itm/Audi-A8-D2...item2c6af945fd

more like this:
http://www.ebay.co.uk/itm/Audi-A3-S3...item43c41596b9

Am I looking at the wrong thing?

Could be part of the difference between Xenons and Bi Xenons...

Yes, could be. The A8 Parts ballast came off a 2000 A8. I think Bi-xenons were later IIRC?

The BI-Xenons have a ballast on the outside and an ignitor inside the lamp. So both of the above :)

I replaced Everything with just a new ballast from ebay with new connections to the bulb socket mostly bc the cost of the oem's

;)

Getting more confused as this goes on! :o

Are these the connections? http://www.ebay.co.uk/itm/2808552182...84.m1497.l2649

And if this is the ballast: http://www.ebay.co.uk/itm/01-06-AUDI...item3f258d7a27

What's the plastic box here? http://www.ebay.co.uk/itm/Audi-A8-D2...item2c6af945fd

And do I need to replace all 3 components?

I used one of these

Ballast

And one of these

Connector

And finally one of these.(only need 1)

Power supply wire

The one that was blown on mine was UK driver side where the ballast is attached to the lamp, the new ballast wont fit onto the lamp so it needs to be placed somewhere behind the lamp. Wires was run true the hole where the old ballast used to sit and silicone was used to seal it.

if i'm not 100% sure but on UK passenger side i think the ballast is placed away from the lamp so that will make this easy and cheap fix easier.

Reason for going with this solution was:
-Unsure if the ballast or ignitor was broken
-To expensive to buy brand new and a used is over priced.
-It seemed that getting the ignitor out would be a pita of unknown dimensions.

Been working smooth for 1.5 years.

You can also use any 35w "slim" ballast but my experience is that they tend to stop working after a while

:)