Design

Design

Bi-Xenon headlight system









Bi-Xenon, a headlight system with moveable reflector, is based on gas discharge technology. The system combines high and low beam into the same lamp.
Due to legal requirements (regarding low beam) for this type of lamp, the vehicle must be equipped with automatic headlamp leveling.
Xenon vs. Halogen
Xenon:
- higher color temperature, which produces a whiter light
- better reflection of road signs and road markings
- lower power consumption (approx. 65% lower).

Good to know:
- Daylight has a color temperature of about 5000 °K. The closer to natural light, the less strain on the eyes. Standard H4 bulb: 3200 °K. Volvo's gas discharge bulb: about 4200 °K.
- With the Bi-Xenon system, high and low beam generates the same light color. The human eye thus has an easier time adjusting to switches between high and low beam.

Bi-Xenon lamp




The light source consists of a discharge tube surrounded by a glass that filters out harmful UV radiation.
- The discharge tube is filled with a blend of chemical compounds, including the inert gas Xenon.
- An electric arch is created through an electrical discharge between two tungsten electrodes.
- Because the lamp does not have a filament, it is less sensitive to bumps and vibrations.
- Bulb designation: D1S.
- Power consumption: 35 W.

Caution! The Bi-Xenon bulb contains mercury (less than 0.5 mg), thus classifying it as hazardous waste. Hazardous waste must be handled in accordance with national legislation. See also Volvo Car Corporation's "Waste Management Guidelines for Dealers."

Position sensor, headlamp leveling




There are two position sensors to enable automatic adjustment of the headlights. Adjustment is vertical depending on load and road conditions to reduce the risk of blinding glare for other drivers.
One position sensor is located next to the rear axle and is connected to the left rear control arm via a link system. The other position sensor is located next to the right front axle and is connected to the right front control arm via a link system.
Vehicle angle is measured by the sensors being actuated via the respective link system.
The position sensors are directly connected to Headlamp Control Module (HCM). Each position sensor has three connections.
Two are used for voltage feed and ground.
One is used for signals about the vehicle's angle.
In ignition position II, level control is active and an average value of the vehicle's angle is calculated using the sensors. At approx. 4 km/h, the dynamic level control is activated, which also performs fast corrections during acceleration and braking. Speed must be above approx. 4 km/h, dark is also required.
The position sensor can be calibrated using the diagnostic tool. The calibration is saved in the headlamp control module (HCM) and must be performed again upon replacement of the control module or position sensor.
There are diagnostics for the position sensors.

Left headlamp control unit (LHCU)/Right headlamp control unit (RHCU) (vehicles with active headlamps only)




A control module is mounted under each light housing on vehicles with active headlights.
Headlamp Control Module (HCM) handles light beam control and active control of the light pattern using Left headlamp control unit (LHCU) and Right headlamp control unit (RHCU). Active control means that the light pattern is turned out to the left or right. Depending on the vehicle's speed and steering wheel angle, how fast and how much the light pattern is turned out varies.
Information is transferred between the left headlamp control unit (LHCU), right headlamp control unit (RHCU) and headlamp control module (HCM) via serial communication.
The lamp housing contains a sensor that indicates whether the light beam has been turned out to the right or left. The left headlight control unit (LHCU) and right headlight control unit (RHCU) send this information to the headlight control module (HCM).
If there is no communication with the Headlamp Control Module (HCM) or a fault arises in the left headlamp control module (LHCU)and/or the right headlamp control module (RHCU), active control stops and in certain cases also the light beam length control.
Then the light pattern goes to so-called "limp home"-mode, in order to not blind on-coming traffic.

Note! Do not adjust the headlight mechanically when the light pattern is in "limp home"-mode.

The left headlight control unit (LHCU) and right headlight control unit (RHCU) can be diagnosed.

High voltage unit




High voltage is required to light the Bi-Xenon lamp.
A high voltage unit is connected to each Bi-Xenon lamp. This transforms 12-V voltage to the approximately 24,000 V required to light the lamp. Once the lamp is on, voltage is lowered to the approximately 100 V required to keep the lamp lit.
Every time that voltage is supplied to the high voltage unit, an attempt is made to light the Bi-Xenon light. If this voltage for a time of 200 ms does not exceed 9.5 V, the light is not lit.
If voltage is too low, e.g., after a power consuming cold start, then the light is not lit just because the engine starts and the alternator begins to charge. Then a new start attempt for the light must be performed by turning the control on the light switch to position "0" or parking light position, and then back to position"2" or "3".
For vehicles on the Canadian market, low beams are activated in all positions for the control on the light switch. If the light is not lit due to the system voltage having been too low, the vehicle must be started again to make a new attempt to activate the light.

Warning! Because of the high voltage it is important to follow the instructions for working with Bi- Xenon lamps and the high voltage unit!