so i have a 2002 a4 1.8t quattro. my car has the xenon HID headlights and couple months ago my left dipped headlight went out. i started to do some research on the what went worng and it turned out to be the ballast. then out of nowhere it my headlight went on and minutes later it went out. so i went without a headlight for about 2 months doing research on finding cheap ballast. In the end i settled and bought a lad5g (the ones that my car needs) from ebay. It works great and no problems until few days ago. 2 weeks with the new ballast and then it went out for 4 seconds while i was driving and the dashboard showed, then it turned on again. It has done that to me twice in two days and its on the same side and its not the bulb itself. Im starting to think that it may be a short circuit somewhere anybody help.sorry wrong group.

 

Brief outage sounds like bulb not installed securely in socket or there is a short or gap somewhere in the wiring or connectors. Especially if the other side does not manifest any symptoms. Or, it could be a crappy Chinese made ballast starting to fail (maybe overheating).