Bulb
The light source consists of a discharge pipe surrounded by glass which filters out damaging UV radiation.
- The discharge tube is filled with a number of chemical compounds including the noble gas Xenon
- A light arc is created by an electrical discharge between two tungsten electrodes
- Because the bulb does not have a filament it is less susceptible to bumps and vibration
- Bulb designation: (special for reflector system).
- Power consumption: 35 W.
| CAUTION | The bulb contains mercury (less than 0.5 mg) and when discarded must be treated as hazardous waste. Hazardous waste must be handled according to the relevant statutory regulations, see also Volvo Car Corporation's "Waste Management Guidelines for Dealers". |
Ballast
An electronic ballast is connected to each headlamp. The ballast functions as a voltage regulator and generates alternative current (AC).
Main tasks
- Light the bulb
- Control the light during operation.
To light the bulb an initial voltage of approximately 24, 000 V is required for a very short time (less than 1ms).
The ballast transforms the vehicles 12 V (DC) to 1000 V (AC).
The high tension switch amplifies the voltage a further 25 times.
When the lamp is lit the voltage is reduced to the 100 V required to keep the lamp lit.
Power consumption: 10 W.
Scheme 2
| 1. | Moving reflector | 3. | Motor, high and low beam |
|---|---|---|---|
| 2. | Controls for reflector | 4. | Position sensor, reflector |
Lighting the headlamp
There is normally a 3 second delay between activation with the light switch or ignition on and the lamp coming on.
- As with normal headlights, the lamps remain off while the starter motor is cranking and come on once the engine is running.
- Each time voltage is supplied to the ballast, 3 one-second attempts are made to light the lamp.
Combined high and low beam
Reflector, left-hand headlamp
Scheme 3
The illustration is a principle sketch showing the different segments of the moving reflector.
The reflector has a complex design where different segments are used depending on whether in high or low beam position.
The reflector is adjustable and can be moved between two fixed points.
- The reflector is moved 2 mm (0.08 in) axially in relation to the bulb
- The direction of the movement means that position of reflector is also moved slightly vertically.
The bulb is fixed.
The headlamp lens is clear.
Automatic level control
Sensor
The following applies to vehicles without Four-C (Continuously Controlled Chassis Concept)
An inductive position sensor reads off the angle between the bodywork and the left rear control arm. The angle is a measurement of how much the vehicle is leaning (chassis height) and is dependent on weight distribution.
- The sensor is mounted differently in FWD to AWD
- The rear electronic module (REM) reads an analog signal (0.5 - 4.5 V) from the position sensor and converts it to an angle value (35°), which is transmitted to the central electronic module (CEM)
- Fully laden vehicles give a signal of 0.5 V which corresponds to minus 35°.
- The central electronic module (CEM) controls the motors for the headlamp range adjustment (PWM signal) and sets the headlamps vertically.
The following applies to vehicles with Four-C
Two sensors read off the angle between the bodywork and the left and right rear control arms. The angle is a measurement of how much the vehicle is leaning (chassis height) and is dependent on weight distribution.
The sensors are mounted differently in FWD to AWD.
The suspension module (SUM) reads the signals from the sensors and converts them to an angle value. The value is transmitted via the control area network (CAN) to the central electronic module (CEM). The central electronic module (CEM) uses this information to control the motors for headlamp range adjustment.
Level control
Controlled at speeds below 4 km/h (2.5 mph)
When the ignition is switched on, the position sensor is read off and the headlamp range adjustment motors set the headlamps.
Controlled at speeds above 4 km/h (2.5 mph)
At greater angle changes during driving the headlamps are controlled. Control is dependent on the time for the system not to react to short term changes such as uneven road surfaces etc.
Calibration
The position sensor must be calibrated after work on the rear suspension. Carry out calibration according to tab DIAGNOSTICS/VEHICLE COMMUNICATION, rear electronic module (REM).
| CAUTION | Calibration must be carried out after work such as removing/installing the sensors and replacing the sensors, rear axle, bushings, shock absorbers or springs. In vehicles with Four C, calibration is carried out via the suspension module (SUM). Beam adjustment is carried out conventionally (via adjustment screws by the headlamp). The light switch must be in the "on" position while calibrating. |
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 tension circuit is broken (for example by a broken cable, blown bulb or no bulb in the bulb connector) the system attempts to activate the lamp for a time of 700 ms. During this time the high voltage is outside the ballast
- Approximate temperatures on the components during operation are; Ballast = 130 °C (266 °F), Bulb holder = 170 °C (338 °F), Bulb = 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 switched off before starting work. Risk of burn injury. The components operate at very high temperatures. |
Scheme 4
- High voltage is required to light the Xenon lamp
- A high voltage unit is attached to each Xenon lamp. It transforms 12 V voltage to approximately 24,000 V, which is necessary to light the lamp. When the lamp is lit the voltage is reduced to the 100 V required to keep the lamp lit
- On each occasion that voltage is supplied to the high voltage unit an attempt is made to light the Xenon lamp. If this voltage does not exceed 9.5 V within a time span of 200 ms the lamp does not light. If the voltage is too low, after a power consuming start for cold start, the lamp does not light until the engine is running and the generator starts to charge. A new start attempt of the lamp must be made by turning the knob of the light switch till "0" position or parking lamp position and then back to low beam again.
| WARNING | Because of the high voltage it is important to follow the instructions for working with the Xenon lamps and high voltage unit |
Scheme 5
| 1. | Motor, high / low beam | Power supply via relay. Reconnected PWM signal provides information about the position of the reflector to the central electronic module (CEM). |
|---|---|---|
| 2. | Motor, headlamp range adjustment | Regulated by central electronic module (CEM) via PWM signal. |
| 3. | Position sensor | Inductive sensor that transmits an analogue signal (voltage) to the rear electronic module (REM) (not vehicles equipped with Four-C (Continuously Controlled Chassis Concept)). On vehicles with Four-C, the signal travels via the suspension module (SUM). |
| 4. | Ballast | High voltage regulator for switch and lamp. |
| 5. | Gas discharge lamp | Socket |
Scheme 6
| 1. | Central electronic module (CEM) | 4. | Motor, headlamp range adjustment |
|---|---|---|---|
| 2. | Rear electronic module (REM) | 5. | Suspension module (SUM) (vehicles with Four-C (Continuously Controlled Chassis Concept) only) |
| 3. | Position sensor |
An electric motor is controlled by the central electronic module (CEM) via a relay (ordinary high beam relay).
The motor drives a gear wheel which moves the reflector along its guides.
A sensor which detects the position of the reflector is connected to the motor.
- The electronics in the motor interprets the sensor information and generates a signal
- The signal is reconnected to the central electronic module (CEM).
If the reflectors are in the wrong position during high beam the reflectors are forced into a safety position
- the warning lamp (orange) lights in the driver information module (DIM)
- an error message is also shown in the display in the driver information module (DIM).
If the high beam is activated with the light switch in 0 position, the high beam is only activated as long as the high beam lever is activated for a high beam flash. The headlamp switch must be in the "on" position in order for the high beam lamps to remain active.