wolywood

On a recent trip with my 2014 A4 I received a loud beep and dashboard message letting me know that my driver's side high/low beam headlight had stopped working. I ordered a replacement xenon bulb (D3S model), and because it was the driver's side bulb and therefore easily accessible, decided to install it myself. I unplugged the old bulb, twisted it counter clockwise to remove it from the headlight housing, plugged in the new bulb, and clicked it back into place. When I started up the car I got the same beep and high/low beam out message as before, only this time there was a second beep and "system fault" message; the driver's side headlight stayed off while the passenger side switched on as normal. As the replacement bulb kit included 2 xenon bulbs I tried installing the second bulb, but got the same result. Am I doing something wrong with the installation, or are the error messages indicative of a more serious issue?

As a side note,the day prior to the original headlight burning out I had driven about 7 hours through a non-stop heavy rainstorm. I did notice some condensation in the driver side headlight casing, though it had evaporated by the next day. Is it possible that rainwater got into the headlight and shorted out something?

SMac770

Do you know the actual DTC codes?
Could be the bulb, or it could be the ballast (the object the bulb plugs into).
You should probably also check the fuse. The left headlamp power stage is by itself on fuse 7 in row 1 in panel C (the panel on the left end of the dash). The right headlamp power stage and all the rest of the headlamp electronics are on fuse 6. Your owner's manual should be able to confirm the fuses.

wolywood

Thank you for the suggestions.

I checked the fuse box, and oddly enough there were no fuses in slots 6 or 7 of row 1 in panel C. The owner's manual confirmed that the fuses should be there, exactly where you said.

The right headlight works, so I'm not sure how it's being powered in my car. The manual did mention that the fuse in slot 12 is also for headlights (and the parking brake) - I checked and that fuse looks fine.

I will purchase a couple of extra 5A fuses today, plug them into 6 and 7 and see if that solves the left headlight problem.

SMac770

Yeah, all the power to the bulbs and motor in the headlamp come from the J519 power control module.
It could be that the fuses 6 and 7, by time 2014 rolled around, was only for manually adjusted range control headlamps (not legal in the US) or for AFS (the bi-xenon with cornering lights).
Along with that fuse 12 in row 1, check the fuses 7, 8, and 10 in row 3. Those all go to the J519 as well.

If the fuses are all good, it would seem trying the ballast would be next.
https://www.ecstuning.com/Audi-B8_A4...dware/Ballast/
Ain't cheap. Might try the classifieds subforum or a junk yard, or even eBay (Chinese roulette).

wolywood

Thanks again for the assistance. I checked the other fuses you mentioned and they are all good. I have ordered a replacement ballast as I am now pretty sure that the storm water condensation in the headlight damaged the original ballast.