Function
Function
Automatic headlight leveling
Position sensors (7/120-121) on the rear and front wheel suspensions send information to Headlamp Control Module (HCM) (4/114) about the vehicle's angle depending on load conditions, acceleration, and braking.
Headlamp Control Module (HCM) uses information from the position sensors to calculate current angle for the headlights.
For vehicles with active headlights and GDL-lights, Headlamp Control Module (HCM) sends information bout current angle to Left headlamp control unit (LHCU) and Right headlamp control unit (RHCU) via serial communication.
The actuators are controlled from Left headlamp control unit (LHCU) and Right headlamp control unit (RHCU).
Active headlamps (vehicles with active headlamps only)
Active headlights are an intelligent headlight system that optimizes lighting of the road surface at night by expanding the light beam. The motorized headlights are controlled by the headlamp control module (HCM), which retrieves signals from the CAN network and from directly connected sensors.
For the active headlight function to be enabled, the headlamp control module (HCM) (4/114) requires information on the following: vehicle speed, current gear, light conditions and steering angle.
The headlight control module (HCM) receives information from the following control modules:
- Brake control module (BCM) (4/16) for information on vehicle speed
- Transmission control module (TCM) (4/28) for information on current gear (automatic transmission)
- Central electronic module (CEM) (4/56) for information from the reversing light switch (3/10) (manual transmission)
- Central electronic module (CEM) (4/56) for information from the twilight sensor (7/12)
- Steering wheel module (SWM), (3/254), information about steering angle
The active headlamp function is only enabled if the following conditions are met:
- The vehicle must be in motion, that is, travel at a speed faster than 4 km/h.
- Reverse gear must not be engaged.
- No daylight light conditions.
In addition, active headlights have to be activated via Light switch module (LSM) (3/111).
When the function is active then Headlamp Control Module (HCM) receives continuous information about the vehicle's speed and steering angle. The vehicle's speed comes from Brake control module (BCM) and information about steering angle from Steering wheel module (SWM).
Using this information, the Headlamp Control Module (HCM) calculates current expansion of the light pattern.
Lighting Bi-Xenon lamps
There is normally a 3 second delay between activation with the light switch or ignition on and the Bi-Xenon lamp coming on.
- As with normal headlamps, Bi-Xenon lamps remain off while the engine is cranking and come on once the engine is running.
- Each time voltage is supplied to the ballast (from the central electronic module (CEM)), 3 1-second attempts are made to light the Bi-Xenon lamp.
Safety
- In the event of a short-circuit on the high tension side the power supply cuts in less than 10 ms
- If the high voltage circuit is broken (such as due to an open circuit, defective bulb or no bulb in the lamp socket), during each activation the system attempts to light the lamp for a period of 700 ms. During the period, there is high voltage across the ballast.
- Approximate component temperatures during operation: Ballast = 130 °C (266 °F), Lamp holder = 170 °C (338 °F), Bi-Xenon lamp = 400 °C (752 °F).
- The glass body of the Bi-Xenon-lamp is filled with different gases and metal vapors which are under pressure. The lamp can explode as it is under gas pressure.
Warning!
- Follow the safety instructions and recommendations in VIDA carefully when working with high voltage.
- Use safety goggles when handling the bulb. Risk of explosion!
- The electrical system must be turned off before starting to work.
- Risk of burn injury since the components operate at very high temperatures.