The combined rain sensor/light sensor is attached to the windshield, near the interior rear view mirror.
The ambient light sensor determines the general light intensity.
For this purpose, it detects the light over as wide an angle as possible, without taking the direction of incidence into account.
The front light sensor determines the light intensity directly in front of the vehicle.
Automatic headlamps
The low beams, side lamps, license plate lamps as well as the instrument cluster and instrument panel illumination are switched on automatically if all the following conditions are met:
- Ignition switch in the "II" or "III" position
- Light switch in the "AUTO" position
- Detected ambient light conditions below a stored threshold value
They are switched on or off by the GEM depending on the input signals of the combined rain sensor/light sensor.
If both the ambient light sensor and the front light sensor simultaneously detect a sudden reduction in light intensity then algorithm-based calculations are performed to determine that the vehicle has entered a tunnel, multi-storey car park or a long underpass.
In this type of case a request to switch on the exterior lights and the display lamps in the instrument cluster is transmitted to the GEM.
If the vehicle is suddenly thrown into the shade by a large truck, the two sensors will register different light intensities. In this case, the algorithm-based calculation will not result in the lights being switched on.
If the vehicle returns to brighter surroundings then the GEM gradually switches off the dipped beam headlamps, side lights, license plate lamps and the instrument cluster and dashboard lighting. Following a request from the light sensor, the GEM first switches off the dipped beam headlamps. After waiting approx. 6 seconds, it then switches off the side lights, the license plate lamps and the instrument cluster and dashboard lighting.
Headlamp switch-off delay
The headlamp switch-off delay utilizes the low beam together with the peripheral lights (if equipped) to illuminate the area surrounding the vehicle. The function is activated by operating the high beam lever when the ignition switch is in the "0" position.
After the last door has been closed, the function remains active for a further 30 seconds and then switches off automatically.
When a door or the tailgate is open, the switch-off time is extended to 180 seconds. After the last door has been closed, the switch-off time is reset to 30 seconds.
The headlamp switch-off delay can be deactivated prematurely by operating the high beam lever again or by switching on the ignition.
The switch-off time is adjusted to set values at the factory and cannot be re-programmed using the diagnostic unit.
Interior lighting
Depending on the vehicle specification, the interior lighting which is controlled by the GEM may include:
- Left and right-hand footwell lamps
- Front and rear dome lamps (in "door contact" switch position)
Depending upon vehicle specification, the interior lamps which can be switched by the operator include:
- Front and rear dome lamps (in "On" switch position)
- Map lights
- Mirror lights in sun visors
- Glove compartment lamp
- Luggage compartment lamp
The GEM-controlled interior lighting is switched on with dimmed brightness if one of the following conditions is satisfied:
- One of the vehicle's doors is opened.
- The ignition key is in the "0" or "I" position and the vehicle is unlocked.
- The ignition key is turned from the "II" to the "I" or "0" position.
The GEM-controlled interior lighting is switched off if all of the doors are closed and one of the following conditions is satisfied:
- 25 seconds have elapsed since the last door was closed.
- The ignition key is turned from the "0" or "I" to the "II" position.
- The ignition key is in the "0" or "I" position while the vehicle is locked.
The duration of the dimmer function is 1.7 seconds in both the switch-on and switch-off phases.
The dimmer function is not used if the interior lighting is switched off by the battery saving function after 30 minutes.
Heated windscreen
Heated rear window and heated external mirrors
The heated rear window and the heated exterior mirrors are switched on by the GEM under the following conditions:
- The heated rear window switch is operated, the ignition switch is in position "II" and the charge warning lamp is switched off.
- The "Defrost" function of the air conditioning has been activated, the ignition switch is in position "II" and the charge warning lamp is switched off.
On vehicles with door modules the GEM transmits the request signal for switching on the exterior mirror heating via the CAN bus to the door modules.
The heated rear window and the heated exterior mirrors are switched off by the GEM under the following conditions:
- More than 14 minutes have elapsed since the switch for the heated rear window was operated.
- The ignition switch is turned to the "0" or "I" position.
- While the heated rear window is switched on, the switch for the heated rear window is pressed or the "Defrost" function of the air conditioning is deactivated.
- The battery voltage has dropped below 10.3 V for more than 20 seconds (power management strategy). Manual requests for switching on the heated rear window by pressing the switch, are ignored at this time.
If the battery voltage returns to the normal range then the disabling of the heated rear window is cancelled - the heated rear window is then in a switched-off state.
On vehicles with door modules the GEM transmits the request signal for switching off the exterior mirror heating via the CAN bus to the door modules.
Windshield wash/wipe system
The windshield wiper system is equipped with just one wiper motor, and this motor is connected to the GEM via a simple cable connection.
The windshield wash/wipe system will only operate if the ignition switch is in the position "I" or "II".
Four wipe functions are available: "Single Wipe", "Speed 1", "Speed 2" and "Intermittent Wipe" or "Automatic Wipe" (depending on the specification of the vehicle)".
In "Speed 1" or "Speed 2" mode, the wipers are operating continuously at either normal speed or fast speed.
When the intermittent wipe mode is switched on the windshield wipers operate at normal speed with the following wiper delays:
- Wiper delay 1: 1 second
- Wiper delay 2: 3.5 seconds
- Wiper delay 3: 6 seconds
- Wiper delay 4: 9.5 seconds
- Wiper delay 5: 15.5 seconds
- Wiper delay 6: 22 seconds
In the event of a failure, the default time for the wiper delay is 3.5 seconds.
When the windshield washer switch is operated washer fluid is sprayed onto the windshield. After a short delay designed to protect the wiper blades the wipers perform 2 or 3 wipes at low speed.
If when the windshield washer switch is activated the windshield wipers are switched off, a single wipe is performed 4 seconds after the wipers have returned to the home position after performing the 2 or 3 wipes.
If the wipers are set to intermittent wipe and the window washer switch is actuated, the wipes are only performed if no further wipe request has been selected via a shorter delay time within the 4-second delay time.
The post wipe function on the windshield ensures that any water remaining on the windshield after washing is wiped away. It is only required if the wipers are switched off or they are set to intermittent mode.
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