today the message center says a bulb is out, left headlight. anyone have a part number for the replacement? i'm a bit confused because some web sites call for the "high beam" replacement. how many bulbs are there, i assume it's my low beam which needs to be replaced.

 

If you have Bi-Xenon headlights then the high and low are the same bulb.
There is a shutter that goes up and down to change the intensity.

To be 100% sure I'd check ECStuning or AudUSAparts and ask them based on your model and VIN.
Be careful in there because there is an igniter that produces very high voltages.

There are a couple threads around on different boards that show how to replace them.
You don't have to go exactly by the Bentley and remove power steering, etc as they say - others have done it successfully but it's a real squeeze in there.

 

finally looked at the bulbs last night. there are two on each side. on both left and right the smaller bulbs, both of which are lit and bright, have hi and low beams. it appears no problem there. on the slightly larger bulbs, one is out and the other shows only a faint glow in the element of the bulb. i wonder if both don't have a problem. what the heck are the larger bulbs supposed to do? are they the parking lights?