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BMW 540i Headlight Upgrades

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The 2003 BMW 540i comes standard with real xenon headlights as I explain here. These are the best headlights available on earth, so of course many people want to upgrade other BMW 5-series and other cars to them. I know I would if I didn't already have them; I've been doing headlight conversions and upgrades with my dad even before I could drive.

In the old days we merely special-ordered the original German-market H4 systems and retrofitted our German cars. Also Hella and others made H4 conversions to retrofit American sealed-bean headlights. In fact, I have a full set of the Hella conversions for the four small rectangular sealed beam system if you'd like them; just contact me. In the old days these were illegal. Today most all cars use the H4 system and are all US DOT approved. Thankfully after over thirty years most US cars actually use the H4 bulbs and are much improved. The US designation for the H4 bulb is 9003.

Real xenon HID is legal and saves lives. It is completely different from any of the simple halogen conversions we've done.

In Europe and Germany the old H4 halogen systems always required, and require to this day, at least manual dashboard-mounted headlight height adjustments to compensate for how the car was loaded. Even the crappiest econobox in Germany has a switch next to the headlight switch labeled "0 1 2 3." One selects a position based on vehicle loading, and true to German style, there is a guide based on passengers and kilogrammes of trunk load for which position to select.

One could get away with a static adjustment for H4 halogen systems, since a 55W H4 bulb on low beam only puts out 1,000 lumens at 3,200 K. A second or two of glare as an aproaching car hit the gas was not going to give you glaucoma.

Retrofitting Original OEM Xenon Headlight Assemblies (Scheinwerferumrüstung, Umbauanleitung und Scheinwerferumbau)

Unfortunately many people presume after all our years of upgrading European cars by ordering the H4 lights that today all you need to do is order the Xenon assemblies for a few thousand dollars and bolt them in.


The Xenon D2S bulbs spit out over three times the luminous flux, 3,100 lumens, and more blue light, with a color temperature of 4,200 K. Unlike H4 halogen systems, a few seconds of glare from a xenon headlight cannot be tolerated. Xenon lights not only require static adjustment, they also require dynamic height control so as a car accelerates the lights don't point up and blind anyone. This complex automatic dynamic height adjustment requires external sensors and is why the xenon assemblies may not simply be bolted in.

Some people confuse careful static adjustment, OK with halogen lights, with the dynamic adjustment needed with xenon. Without automatic dynamic height control you'd need to adjust the lights even further down statically for enough safety margin to avoid glare when you hit the gas. This would defeat much of the purpose of the xenon lights!

BMW 540 suspension height sensor

2003 BMW 540i rear suspension height sensor (click to enlarge)

Xenon lights with automatic dynamic height adjustments and washers allow manufacturers to raise the static adjustment height, giving more seeing distance while still preserving other people's eyesight. If you throw the real xenon headlight assemblies into a car that didn't come with them it won't have the correct height sensors on the suspension and data piped in from the DSC systems to activate the automatic dynamic height adjustments. The headlight assemblies won't work correctly without the sensor inputs. Headlight washers are required since the glare goes way up when the lenses are dirty, so you'll also have to add those.

I know you hackers figure you'll just adjust the xenon assemblies carefully, but that's bad since every time you hit the gas or load up the trunk you'll be blinding people. Don't even think about retrofitting xenon headlight assemblies unless you have this automatic dynamic control and washers. Dynamic control figures in not just acceleration, braking and suspension position; it also factor in road speed so it knows how to interpret suspension variations.

The dynamic levelers are impressive. I've been studying auto lighting for over 30 years, and with this much experience I giggled with excitement when I first saw my BMW xenons automatically adjust as I drove. It's the first time I've seen something this innovative in decades.

I have seen retrofit kits from BMW to do this, which also require the addition of washer assemblies and level sensors in the wheelwells. Try bmwtips.com or your dealer's parts department to see if you can learn more.

Illegale Xenon-Nachrüstung ist gefährlich und verboten

That's German for "Illegal xenon bulbs are dangerous and forbidden."

Some boneheads like to jam true HID xenon bulbs into existing housings designed for halogen bulbs. This is illegal and probably also nullifies any liability insurance on your car. This is because light assemblies are designed for certain types of bulbs, and the gaseous discharge from xenon bulbs is very different from the hot wire of a halogen bulb. Thus a xenon bulb will throw light into all the wrong places if simply jammed into an existing headlight designed for a regular bulb. Don't do this. Even worse, xenon bulbs only have one light source for one beam only. Real xenon headlights have separate bulbs and reflectors for high beams and another set for low beams. Halogen bulbs usually have a high and a low beam filament in the same bulb. People selling these illegal xenon conversions try to get you to believe that you'll have so much light you won't need your high beams. Wrong! Don't do this.

Don't Use Blue-Painted Halogen Bulbs

Don't confuse the real xenon BMW lamps with blue-painted halogen bulbs used by ghetto kids to make lots of glare and imitate the whiter light of xenon HID. Many of these fake bulbs say xenon on them, like these here. These blue-painted bulbs are just popped into existing headlights. Since most ghetto cars have severely weathered and yellowed lenses they throw almost all the light into the eyes of onlookers, impressing others in parking lots but getting little light on the road. Even worse, these fake bulbs are made a bit smoky so that they diffuse a lot of light away from the road and up into your eyes as glare even if you had new lenses.

These fake blue bulbs say all sorts of things like laser xenon white, 15,000 Kelvin, 55W = 135 Watt light output, etc. If you actually look at the engineering data which isn't on the box you'll notice that because of the blue paint these bulbs actually churn out fewer lumens!

Don't do this. Here's an excellent page devoted to explaining why these are so bad.

Summary: Don't do This.

Sorry to spoil your party, especially since I'm also a hacker at heart, but the only real way to get decent xenon headlights is to buy a car that comes with them from Germany or possibly Japan. Everything else is either not going to work well, and more likely is illegal because it won't work well.

Why should you care? Few people drive on dark roads without street lights anyway.

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