Hi
well what happened was...
My xenon dipped beam stopped working so I took it to an Audi Specialist for them to investigate the cause. They told me that the ballast wasn't working and that Audi don't sell ballasts separately so it would cost me a new headlight at ~£600; they then suggested I source my own ballast
So I sourced my own ballast;
http://www.ebay.co.uk/itm/400517775232?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
I then decided to fit the new ballast my self. The old ballast has the high voltage cable to the HID bulb routed through the underside of the headlight unit through a small ~1"x1" plastic doorway; the plastic door is integral to the ballast and clips into the headlight to form a seal and cannot be removed from the ballast unless I were to careful unwire the ballast --- the ballast was apparently broken so I just cut the high voltage HID cable either side of the plastic door and clipped the door back into the headlight so I still had a sealed headlight unit.
Again I have no way of routing the new ballast in through that little plastic door unless I unwire the new ballast and thread the cable through the hole. What the new ballast does have though is a large rubber grommet; so I can cut a large hole in the back cover of the headlight unit and route the cable in through the back rather than the underside as before - I haven't done this yet.
Before I start cutting things I decided to test if the ballast actually worked - it didn't! Still no light. That was last weekend by which time I was so angry with myself for not testing it prior to cutting the old one out I put the car back together.
Then last Monday I read that the polarity of aftermarket ballasts can sometimes be reversed so yesterday I got back to it.
However before I reversed the polarity I decided to test the voltage in the 12V power supply to the ballast (this should have already been tested by the garage that told be the ballast was broken) F**K!!!!! 0volts. So I've butchered a perfectly decent Audi headlight @~£600 because the Audi Specialist has misinformed me!
So I then test the electrical continuity from the 12V xenon wiring in the headlight and its fine; I check the continuity of the headlights earth wiring and its fine! So the wiring inside the headlight is absolutely fine.
Then I decide to check the voltage across the pins on the wiring loom connector that connects to the headlights and I find that the pin for the Xenon (dipped beam) has no power to it whilst the sidelight gets a healthy 11.6V. Just to double check I check the working passenger side Xenon and the connector had a good 11.6V.
So to summarise I have butchered a working headlight ballast on the advise of an Audi specialist when in fact the headlight wasn't getting any power which they should have identified in about 20seconds when I left it with them to check the cause of my broken lights.
So I am now stuck with having to butcher my headlights even more to route the aftermarket cabling in through the back cover and still I need to find the cause of why the wiring loom has no power
@t8ups If you do have any words of advice or sympathy they will be kindly received. Could I splice the HID cabling on my old ballast back together?