Technical Training
Headlamp Assemblies, Standard Equipped
The Headlamp Assemblies contain the Low Beam and High Beam bulbs. Both bulbs are 12v 55w H7 type bulbs. The bulbs are replaceable from the rear of the headlamp assemblies.
Headlamp Assemblies, Xenon Lights (Optional)
The automotive industry/press often identify xenon lighting systems as HID (high intensity discharge) systems. Xenon headlight technology was first introduced to the US market exclusively on the E32 750iL in 1993. BMW xenon headlight systems have evolved and their availability as optional equipment has spread throughout the model lineup. Blue/White in color and using ellipsoidal technology Xenon headlights provide improved night time visibility in all driving conditions compared with traditional Halogen bulb head-lights.
Principle of Operation
Headlights
Low beams are switched on when the main light switch is set to position 2 with the ignition switch in position 2. Pulling the low beam/high beam switch towards the driver with the ignition in position 1 or 2 activates the headlight flasher (flash to pass). Flash to pass is active with the low beams OFF or ON.
High beam lights are activated by pulling the low beam/high beam switch toward the driver until its end position is reached. Pulling the switch a second time de-activates the high beams. The low beam lights must be on and the ignition switch in position 2 for high beam activation. Operation of the optional Xenon headlights is the same.
Xenon headlights provide the following benefits:
- Longer bulb life. Typically, xenon bulbs will last from 3 to 5 times longer than halogen.
- More light output. Xenon headlights produce from 2.5 to 3 times more lumens than halogen.
- Blue/White light (simulates natural daylight). Xenon bulbs produce a blue/white light while halogen bulbs produce a yellow light. The light color of a light source is measured in color temperature (not to be confused with thermal temperature). Color temperature is measured in Kelvin (K). The higher the color temperature the whiter the light.
Natural daylight = 4,500 to 5,000 K
Xenon headlights = 4,000 to 4,500 K
Halogen headlights = 3,200 K (yellow in color)
- Better driving visibility. The combination of higher lumens and higher color temperature provide a superior lighting source. The beam is wider and brighter in front of the vehicle than conventional halogen bulbs improving safety and driver comfort.
- Lower operating temperature.
- Lower power consumption.
The BC1 provides control over exterior lighting and illumination of instrumentation indicators for turn signals and high beams. The exterior lighting functions of the BC1 also provide "Follow-Me-Home" Lighting and emergency operation of limited lighting functions in the case of BC1 failure. These light functions are controlled by the BC1:
- Headlights
- Tail Lights
- Brake Lights
- Turn Signals
- Side Marker Lights
- Auxiliary Lights
- Fog Lights
- Directional Indicators
- High Beam Indicator
- License Plate Lights
- Hazard Warning Lights
- Flash to Pass Lights
The BC1 does not control, but signals for activation the optional Xenon Lights.
Xenon bulbs are identified as D-2S (D= Discharge). Xenon bulbs illuminate when an arc of electrical current is established between two electrodes in the bulb. The xenon gas sealed in the bulb reacts to the electrical excitation and heat generated by the current flow. The distinct bluish/white brilliant light is the result of the xenon gas reacting to the controlled current flow.
Phases of Bulb Operation
Starting Phase: The bulb requires an initial high voltage starting pulse of 18-25RV to establish the arc.
Warm Up Phase: Once the arc is established the power supply to the bulb is regulated to 2.6A generating a lamp output of 75 watts. This is the period of operation where the xenon gas begins to brightly illuminate. The warm up phase stabilizes the environment in the bulb ensuring continual current flow across the electrodes.
Continuous Phase: Once the warm up phase is completed, the system switches to a continuous mode of operation. The supply voltage for the bulb is reduced and the operating power required for continual bulb illumination is reduced to 35 watts which is less than a conventional halogen bulb.
Functional Description
To regulate the power supply to the bulbs, additional components are required. The xenon control modules (1 per light) receive operating power from the BC1 when the headlights are switched on. The xenon control modules provide the regulated power supply to illuminate the bulbs through their phases of operation. The igniters establish the electric arcs. Integral coils generate the initial high voltage starting pulses from the control module provided starting voltage. Thereafter they provide a closed circuit for the regulated power output from the control modules.
Xenon Headlight Testing
Warning: Xenon headlight control systems generate high output voltage. Prior to headlight removal or testing observe the vehicle warning labels and be cautious by following safeguards to prevent accidental injury.
Use test adapter 90 88 6 631 010 for testing of Xenon Lights. The DISplus Measurement System includes all the cable connection information as well as Test Modules.
Dynamic Headlight Adjustment (DHL - Xenon Only)
Cars equipped with Xenon headlights require automatic headlight aim control; this necessitates a separate control module to carry out automatic adjustment of the headlights. With automatic headlight leveling, the load status and its changes are recorded by means of two height level sensors (potentiometers) located at the front and rear axles. The information from these sensors is communicated back to the DHL module.
Each headlight has electrically driven linear stepper motors, which are connected to the headlamp inserts in such a way that their movement changes the range of the headlamp.
DHL Headlight Adjustment Control Module is located under the dash on the drivers side.
Bi-xenon light
At BMW, the bi-xenon light now replaces the conventional headlight with H1 lamp bulb.
An electric arc is produced in the D2S/R lamp.
The bi-xenon light system is of redundant design as for conventional headlights. Faults or damage in the area of one headlight do not result in malfunctions in the other headlight.
In the case of high beam, the halogen lamps are supplemented by an enlargement of the focus angle of the xenon driving light. To create the high beam distribution, a mechanical, electromagnetic plate is folded back by an actuator drive. With the driving light switched on, this plate covers part of the reflector, reducing the lighting intensity and/or the focus angle.
MINI: For the MINI, the headlight has a conventional design. No xenon high beam is cut in by the xenon control module. In the case of halogen high beam, the xenon driving lights remain active.
The headlight flasher still uses the halogen bulbs.
The xenon control module for the MINI is not diagnosis-capable.
CAUTION!
Relevant safety and accident prevention regulations must be observed when conducting all tests and work on the xenon light system. The xenon light headlight system carries dangerous high voltages!
Bi-xenon headlight
Bi-xenon headlights consist of
headlights with D2S/R bulbs (bulb with a xenon gas charge)
an electronic control facility (ignition device and control module)
Electrical control facility for bi-xenon headlights
The electronic control facilities consist of
bi-xenon control module and
bi-xenon ignition device. The ignition unit generates the high voltage necessary for igniting the electrical arc in the lamp.