Lighting - Design and Function (Xc): Other Volvo V70 II

Bulb

The light source consists of a discharge pipe surrounded by glass which filters out damaging UV radiation.

1. The discharge tube is filled with a number of chemical compounds including the noble gas Xenon
2. A light arc is created by an electrical discharge between two tungsten electrodes
3. Because the bulb does not have a filament it is less susceptible to bumps and vibration
4. Bulb designation: (special for reflector system).
5. Power consumption: 35 W.

Ballast

An electronic ballast is connected to each headlamp. The ballast functions as a voltage regulator and generates alternative current (AC).

Main tasks

1. Light the bulb
2. 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.

Function, GDL bulbs

See Function

Scheme 264

Scheme 265

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.

1. The electronics in the motor interprets the sensor information and generates a signal
2. 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

1. the warning lamp (orange) lights in the driver information module (DIM)
2. 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.

Scheme 266

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 headlight levelling.

Xenon vs. Halogen

Xenon

1. higher color temperature, which produces a whiter light
2. better reflection of road signs and road markings
3. has lower power consumption (about 2/3).

Good to know

1. 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.
2. 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.

Lamp

The light source consists of a discharge tube surrounded by a glass that filters out harmful UV radiation.

1. The discharge tube is filled with a blend of chemical compounds, including the inert gas Xenon.
2. An electric arch is created through an electrical discharge between two tungsten electrodes.
3. Because the lamp does not have a filament, it is less sensitive to bumps and vibrations.
4. Bulb designation: (special for reflector system).
5. Power consumption: 35 W.

An electronic ballast is connected to each headlight. The ballast serves as a voltage regulator and generates alternating current (AC).

Primary tasks

1. Light the bulb.
2. Regulate light during operation.

A initial voltage of about 24,000 V for a very brief period (less than 1 ms) is required to light the bulb.

The ballast transforms the vehicle's 12 V (DC) to 1000 V (AC).

The high voltage contact amplifies the voltage an addition 25 times.

Once the bulb has been lit, voltage is regulated down to about 100 V, which is required to keep the bulb lit.

Power consumption: 10 W.

See Function

Scheme 267

Scheme 268

An electric motor is controlled by the central electronic module (CEM) via a relay (standard high beam relay).

The motor drives a gear that moves the reflector along its guides.

A sensor connected to the motor detects the position of the reflector.

1. The motor electronics interpret the sensor information and generate a signal.
2. The signal is fed back to the central electronic module (CEM).

If the reflectors are in the wrong position for high beam, the are forced down into a so-called safety position

1. the warning lamp (orange) in the driver information module (DIM) illuminates
2. an error message appears in the driver information module (DIM) display.

If high beam is activated with the light switch in position 0, high beam is only activated while the stalk is in the high beam position, so-called high beam flash. In order for high beam to remain on, the light switch must be in the "On" position.

Scheme 269

The left headlight control unit (LHCU) / right headlight control unit (RHCU) are located within the headlights.

The left headlight control unit (LHCU) / right headlight control unit (RHCU) handle the active regulation of the light beam. Active regulation means that the light beam is turned out to the left or right. The light beam is turned out at different amounts and different rates depending on vehicle speed and steering wheel angle.

Information is transferred between the left headlight control unit (LHCU), right headlight control unit (RHCU) and headlight control module (HCM) via LIN 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 headlight control module (HCM) or a fault arises in the left headlight control unit and/or the right headlight control unit (RHCU), active regulation ceases. If this is the case, the headlights are aimed straight ahead.

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

Reading off input and output signals

This function can be used to continuously read off the status of the control module's input and output signals.

For more information about parameters, see Vehicle communication information in Specifications, other.

Activating components

This function can be used to activate components to check that they are working.

For more information on activations, see Vehicle communication information under Specifications, other.

Downloading software and replacing the control module

New software can be downloaded to the headlight control module (HCM).

When ordering software the vehicle's hardware and software are compared with Volvo's central database. If the comparison is correct the software is downloaded to the control module.

If the comparison between the car and Volvo's central database does not correspond, then the database is updated with the vehicle's configuration. When this is complete the software is downloaded.

For further information regarding downloading, see Design and Function, Downloading Software.

Scheme 270

Active headlights are an intelligent headlight system that optimizes illumination of the road surface at night by turning out the light beam. The motorized headlights are controlled by the headlight control module (HCM), which retrieves signals from the CAN network.

In order to activate the active headlight function, the headlight control module (HCM) (4/118) needs information on the following: vehicle speed, current gear, light conditions.

The headlight control module (HCM) receives information from the following control modules

1. Brake control module (BCM) (4/16) for information on vehicle speed
2. Transmission control module (TCM) (4/28) for information on current gear (automatic transmission)
3. Central electronic module (CEM) (4/56) for information from the reversing light switch (3/10) (manual transmission)
4. Central electronic module (CEM) for information from the twilight sensor (7/12)

The headlight control module (HCM) is activated automatically when the ignition switch is turned to position II. In order to turn out the light beam, the following conditions must be fulfilled

1. The vehicle must be in motion, that is to say travelling at a speed greater than 3.6 km/h (2.2 mph).
2. Reverse gear must not be engaged.
3. No daylight light conditions.

The switch for active headlights on the climate control module (CCM) (3/112) can be used to disable/enable the function.

When the function is active, the headlight control module (HCM) receives continual information on vehicle speed and steering angle. Vehicle speed is obtained from the brake control module (BCM) while steering angle information comes from the steering wheel angle sensor module (SAS) (3/254). This information enables the headlight control module (HCM) to calculate the current turn-out of the light beam.

Scheme 271

Note. Changing light pattern and limiting active control is only permitted on certain markets. The function is controlled by the software in Headlamp Control Module (HCM).

If the vehicle is designed for right-hand traffic and is used in a country where traffic drives on the left, the light beam must be shifted and active control limited so as not to blind oncoming traffic. This also applies if the vehicle is designed for left-hand traffic and is used in a country where traffic drives on the right.

In order to change the setting, hold the active headlight switch on the climate control module (CCM) depressed for at least five seconds.

When the setting has been changed, a message appears in the driver information module to indicate the current setting (for right-hand or left-hand traffic) of the vehicle.

When the setting has been changed and the vehicle is in "tourist mode"

1. When driving straight ahead, the light beam is turned in a suitable direction so as not to blind oncoming traffic.
2. As before, the light beam will also be turned out in the suitable direction when cornering, just not as much.
3. The light beam is also aimed down slightly (shorter beam length) so as not to blind oncoming traffic.

The vehicle must be stationary when the setting is changed.

Note. The light beam must under no circumstances be adjusted with the adjuster screws when in "tourist mode". If the light beam is adjusted with the adjuster screws when the system has aimed the headlights down, there is a substantial risk that the vehicle will blind oncoming traffic when the system resumes normal mode.

Scheme 272

The most important task of the headlight control module (HCM) is handling the active headlight function.

The control module is mounted beneath the driver's seat. The entire control module is removed from the vehicle upon replacement.

The headlight control module (HCM) communicates both with directly connected components, and with other control modules via CAN communication.

The control module checks activations and input and output signals using an integrated diagnostic system A diagnostic trouble code is generated if the control module detects a fault. In certain cases the control module replaces the faulty signal with a substitute value.

Any diagnostic trouble codes are stored in the relevant control module memory. The data can be read off using a diagnostic tool.

If the control module detects a fault, a diagnostic trouble code is registered in the control module's internal memory. At the same time, a number of values that were frozen when the fault occurred are store. Depending on the severity of the fault, some functions will be fully or partially disabled. A warning or information text will appear in the driver information module (DIM) display. In addition, the LED in the active headlight button will flash. Diagnostic trouble codes and frozen values (detailed diagnostic trouble code information) can be read with a diagnostic tool via the data link connector in the vehicle.

In order to check whether the headlight control module (HCM) is supplied power and is grounded, the ignition switch can be set to position II.

For further information, also see Signals .

Signals

The chart below summarizes the input signals to and output signals from the headlight control module (HCM). The signal types are divided into LIN communication and CAN communication. The illustration below displays the same information with the Volvo component designations.

Scheme 273