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20 Electrical system
9-5
Description of operation
General
The headlight contains a xenon lamp with ignition
transformer, control module, beam length
adjustment motor, H7 halogen bulb and parking
light bulb.
A 70mm (2.75in) ellipsoid lens forms the light
pattern together with the xenon lamp and
reflector. The headlight is equipped with a clear
plastic protective lens that does not refract the
light.
There is a halogen bulb mounted in the headlight
assembly housing. When the headlight flashers
are used while the low beam is turned off, only
the halogen bulb lights up (sometimes called the
“flash to pass” function).
Xenon lamp
The xenon lamp is a gas discharge lamp and
therefore does not have a filament. The light is
generated by an electrical discharge between two
electrodes. The igniter is the capsule in which the
discharge takes place and is filled with xenon gas
and metal halogens under high pressure. The
discharge generates a large amount of visible
light and a certain amount of ultraviolet radiation.
The xenon lamp has an outer casing that reduces
the dispersion of ultraviolet radiation.
The xenon lamp is driven by the AHL control
module. The control module sends high voltage
pulses to the ignition transformer for turning on
the lamp. The ignition transformer, which is
integrated in the xenon lamp, generates the
ignition voltage (approx. 23,000 volts) that is
required to turn on the lamp. Once the discharge
is in progress, the voltage requirement will drop
to around 85V. The AHL control module governs
the current/voltage supply to the lamp.
Important
Make sure to use only lamps with the correct
output when changing or some components
may be damaged.