BMW part 63126929309 („Bulb socket with bulb f parking light“), the lamp for illuminating the corona of the headlights, is quite expensive. Drawing: Part #5 here at bmwfans.info or here at leebmann24.
It is also not very bright, but in return at least yellowish… You better exchange it for an LED „burner“ with al least 5 Watts – unless you have stupid local regulations regarding exterior lights to obey, of course.
The LED-version might trigger a „check control“ warning because of the altered current flowing through it. Better lamps don’t do this. They do however flash, when the car tries to measure the „wire“ resistance while the lights are off (you can code „KALTUEBERWACHUNG_SL_V_R“ or „KALTUEBERW_SL_V_R“ and „…SL_V_L“ in „LMA“ off to avoid that).
Or maybe you just want to replace the illuminant without paying off Hella and BMW for that insolent welding spot preventing you from keeping the socket? You can.
There is a bayonet style socket inside. A BA9s 12V 10W bulb will do – not that easy to get, but not impossible. To get a recess into the reflector (without chipping the coating) I clamped a round key file into my cordless drill. Afterwards the bulbs can be exchanged via the socket.
(Original post: http://www.metalforum-owl.de/viewtopic.php?f=21&t=138&start=80#p39616, July 8th 2011)