HID Kits, Xenon Bulbs and Halogen headlamps -- The Story
So I've done a handful of research lately on halogen and Xenon lights. Below is a basic summary of my findings when investigating (and eventually buying) replacements for my stock Halogen headlamps in my 2006 Mercedes C55 AMG.
Disclaimer: I pulled this together from bits and pieces here and there. I do not claim to be an authority on lighting, but I think most of this is reasonably accurate.
Info about Xenons
HID = High-Intensity Discharge (for purposes of this doc, HID == Xenons)
HID Kit == Xenon Bulb (mine are size 'D2S' for low beam, H7 for high beam) + Ballast + Wiring.
If you already have headlamps with HIDs or are replacing the bulbs in an existing HID with a different color / temperature you do NOT need a whole new kit, just new bulbs.
Higher temperature == more color and less light
Stock color / temp is 4300Kelvin. 5000Kelvin is a brighter white, 6000K starts to look a bit blue and 8000K is getting fairly blue. I went with 8000K 🙂
HID kits are generally a bit flaky, but are very cheap
Stock halogens are 35W, and to avoid complications its not a bad idea to stick with 35W if your upgrading to Xenon. If the ECU notices a different power draw from the headlights it might throw errors.
Mercedes should be coded from Xenons (via STAR / ODBII computer systems) to avoid error codes.
Info about upgrading from Halogens to Xenons
If you have halogen lamps you can take out the halogens, buy an HID kit and be good to go, total cost of upgrade on the order of a couple hundred bucks (2-300) TOPS.
HOWEVER -- You could also replace the whole headlamp assembly, which has several advantages:
Stock halogen headlamps do not use projector lenses. Projector lenses look significantly better with Xenons than the traditional ones.
OEM Xenon headlamp kits come with their own ballast etc. which is generally more reliable than a HID Kit.
Mercedes OEM Xenon lamps have leveling motors etc, which is a nice to have but a bit gimmicky.
I bought a used OEM Xenon assembly from a friend on mbworld.org -- going to install them later this week. Hoping for the best!