The first small orange light on the left is the turn signal.
Parking and standing lights are the two larger rings around the headlights.
The next light is the xenon low beam. It's just the the small gray circle inside a larger cosmetic ring. The active part of the projector assembly is only 2-3/4" in diameter. It's a refractive system.
The conventional reflective halogen high beam is the last one on the right. It's about 4" in diameter.
The twin nubbins on the bumper are the two high pressure washer jets .
The xenon low beam adjusts continuously and automatically with a small opaque shade that moves up and down inside the low beam. You can see this as you tap the brake or the throttle.
The halogen high beam adjusts by pivoting the entire high beam reflector assembly. You can see them adjust when you first turn the key in your 540.
Better than a Boeing 747's Landing Lights
The standard xenon low beams are better than the landing lights of a Boeing 747. The BMW lights up the entire road brilliantly and creates no glare. Aircraft landing lights are just spot beams like a big flashlight. The BMW by comparison washes the entire road from far left to far right in brilliant, even light.
I'm serious. The best landing light used on large jets is the General Electric Q4559X (mfr p/n 42552 which you can get here for $30) or Sylvania model 56223. It's an 8" diameter, 600 watt, 28 volt PAR64 quartz-halogen sealed beam. More here about it. It only has a life of 100 hours and is nothing more than a 600,000 candle power spot pencil beam. 747 landing lights are cheap: $30 gets you the complete conventional halogen bulb, sealed lens and reflector.
The BMW lights, which cost over ten times as much, use real xenon gaseous high-intensity discharge (HID) bulbs with a life of 2,700 hours. 747 landing lights use regular halogen bulbs which simply heat up a wire for light and burn out quickly.
The BMW headlights have a sharp cut off, so even though they light the road as if it were daylight no glare goes into anyone's eyes. They don't have the chromatic aberration of lesser lights that leads to a bluish transition from light to dark that throws nasty blue light into oncoming drivers eyes.
it is normal for the xenons to take 15 seconds to warm up. The instant you turn them on they will be a dull blue. Even in these first seconds they are still as bright as the halogens or fake xenons, and just get brighter from there.
Automatic Dynamic Range and Height Adjustment
This is the magic part about the real BMW xenon headlights. They impressed the dickens out of me on my first night drive. I'm used to lights dipping as I brake and rising as I hammer it. These automatically and dynamically adjust the lights as you drive!
The BMW xenon lights continuously adjust themselves as you drive. As you put more or less in the trunk, step on the gas or brake or drive up or down hills in normal cars the lights go up and down, and half the time would blind oncoming drivers. If you load up the trunk in a normal car or every time you step on the gas the car points up a little and points the lights up. In the BMW 540 the xenon lights automatically self adjust, and if you're paying attention as I do you'll see them moving up and down to compensate every moment as you drive. This is also why it's illegal to jam a xenon conversion bulb into a regular headlight: the xenon is so much brighter that it's a safety hazard if it doesn't continually adjust itself. This is why the xenon headlight assemblies on the BMW cost about $1,000 each.
The adjustment considers acceleration, braking and suspension positions. It also considers road speed so it knows how to interpret suspension movement.
Self Steering Lights
Steered headlights were first available from Auburn and Duesenberg in the 1930s; they were paired driving lights that connected via linkage to the steering knuckles. They were also available as accessories for other cars. The 1948 Tucker Torpedo was the first mass-market car to have headlights that turned as one went around corners.
This was forgotten for years until it was copied today by the Acura RL and the newest BMWs.
The 540 doesn't need any of this since it fully illuminates the entire road from far left to far right. That's an advantage of the large amount of light that comes out of the xenon bulb. It's nit just about needless brightness; it's about getting light to where it needs to go.
Xenon D2S Bulbs
Real HID bulbs have no filament, are perfectly clear, need 25,000 volts to fire them off, have a circular connector and a life of about 2,700 hours. See a picture here and more info here. Also see here for lots of great general info on automotive lighting. The headlight into which you insert the bulb is another complex assembly.
The xenon Osram XENARC D2S bulb (66040 UVS 35W P32D 10X1) makes 3,200 lumens of light from 35 Watts of electricity. By comparison, an H4 halogen low beam only makes 1,000 lumens from 55 Watts, and the illegal blue-painted "Genuine 100 Watt HID Xenon effect!!" ones make even less due to the blue paint.
Life of the xenon D2S is 2,700 hours, compared to 300 hours for ordinary halogen headlights and 100 hours for a premium 747 landing light. The Osram Silver Star high-performance H4 halogens smoke out after just 24 hours, which is why auto parts dealers love to sell them to kids. Thus the xenon bulbs should last as long as your car. D2s is about 4,200K and halogen is about 3,200K. Here's some more info on HID.
I'll never need to replace these, however a reader writes to suggest that HIDplanet.com is the best place to get the best Philips D2S bulbs for $75, the pair!
The same reader prefers the color of Philips over Osram bulbs. He's seen Osrams tend to be pinkish, while the Phillips are white. The Philips start off yellowish for the first 100 hours and turn to completely white.
Forget any idiotic other brands which just spike the gas mix or paint them to look other funny blue or violet colors. You want 4,200 Kelvin. Higher (bluer) color temperatures are just gimmicks. See also my page on illegal bulbs here.
The BMW 540i needs no wipers. It uses an extremely high pressure stream to blast any and everything off the lenses. I don't know if it's also heated to melt off ice and snow. I live somplace warm.
Automatic Headlight On/Off Control
This is the automatic control which swtiches the lights on and off as needed. I keep this off, since it lights off my xenons coming out of the garage in the middle of the day. Xenons don't wear out by use; they burn out from repeated starts.
The high beams are conventional 55W H7 halogens. The low beams stay on and these turn on to fill in the further away part of the road. Honestly since the xenon low beams are so spectacular the high beam halogens don't add much. Mercedes has added bi-xenons to the newest models. The problem with xenons is they must be turned on and left on. They take time to warm up, and they are also worn out by constant on and off cycles. Thus for use in high beams I'm guessing Mercedes leaves them on all the time and just uses a shutter.
Because the Xenon low beams are so spectacular the 35 W H8 halogen fog lights (Nebelscheinwerfer) don't do much. You may safely ignore them since they are overpowered by the extraordinary low beams. If you has a lesser model without the Xenon low beams you might need the fog lights.
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