Can you post a pic of what it is that you are having difficulty figuring out? BMW uses a lot of similar design elements...especially when it comes to wiring harnesses and connectors. Someone may not have opened or seen the headlight set-up for an e70 X5...but may be familiar with the harness if it is like other ones used around the vehicle or even other models. :)

Yeah, I finally installed the E55 projector in my E39 headlights. Nothing fancy, just cleaned up the factory E55 projector lenses, kept everything else stock. Very clean looking but I wish there was a little less light on the road directly in front of the front bumper.

Okay, I managed to get a little more light to the area (passenger side) and was able to see enough of the spring to release it. Local Advance Auto Parts store wants $99 for a D1S, and I'm not even sure the bulb is the culprit. Maybe I'll swap with the driver's side to see if it's bulb, ballast, or circuit first, then order my parts online for less. Even if cheaper online parts are not as good, at least I can justify some "try & see if it fixes it".

Any of the bulbs mentioned above are good and the Retrofit Source, among others, is a great online supplier of HID bulbs. No worries about counterfeit bulbs from there.

Swapped the bulbs. They both work in the driver's side socket. Guess now I'm looking at a ballast. Trying to figure out where the darn thing is & how to access it. Thinking I'll have to remove the front section of wheel well. Anyone familiar with this?

I did a DIY on it if you want to check it out!

https://www.youtube.com/watch?v=0w2iLOnVJe8

Thanks, Ortho, for posting the DIY of the bulb changeout. Will no doubt help someone. Unfortunately, my bulb is not the problem, so proved by swapping the bulbs L&R. Finally last night I probed the wiring harness with a volt meter and found that I do have 12V going to the headlight assembly (15V, with the motor running -- wow!). Pretty certain that means it's the ballast. I haven't been able to get the headlight assembly out to access the ballast. I've read that some say I must remove fender & bumper cover, while some say it's not necessary. I've unbolted the fender but it doesn't budge. I can see the ballast on the bottom of the assembly, but I don't think I can get to all the screws and change it out unless I remove the assembly. I'd like to be able to remove it anyway to replace the lenses (found a good deal on those, so I want to replace rather than refinish). So wish I had a DIY video on removing these headlight assemblies!

I've seen a couple of headlight assembly removals on youtube. Two of them that I had seen took it out through the wheel well and removed wheel.

Sure wish I could find them. Only one I've found, the guy gave up and broke the old lense up and replaced it with the assembly still halfway in the vehicle. :(