Rain/Light Sensor

Rain/Light Sensor





A rain/light sensor is available as an option on the (E85) Z4. The headlights are switched on/off automatically by the rain/light sensor according to the ambient light conditions. The rain/light sensor detects the presence of water on the windscreen and switches the windscreen wiper on and off accordingly.
The rain/light sensor is fitted in the base of the rearview mirror and it consists of optical sensors. The RLS has 2 optical sensors integrated in the casing of the automatic interval control module. The 2 new sensors supplement the otherwise unchanged wiper interval control function of the automatic interval control module as follows:
^ An ambient-light sensor detects the light intensity above the vehicle within a wide scanning angle.
^ A forward light sensor detects the light intensity within a narrow scanning angle directly ahead of the vehicle.
An internal processor calculates from the readings taken by the ambient and forward light sensors whether the preconditions for switching on the lights are present.
The RLS checks the following preconditions for switching on the headlights:
^ Twilight
^ Complete darkness
^ Entry in underground car park
^ Entry in tunnel
If any of the above conditions is met, the rain/light sensor on the (E85) Z4 sends the information via the Kbus to the light switch centre. In order to be able to control the headlights automatically, the rain/light sensor must be activated by a separate light switch setting on the light switch centre.
If the light switch on the light switch centre has been set to the position for automatic control of the headlights, the exterior/instrument panel lights are switched on by the light switch centre. The preconditions for switching on the lights are as follows:
^ One of the rain/light sensor conditions listed above is met.
^ The fog lamps are switched on.

Note: If the above conditions exist, the lights can only be switched off by switching off the fog lamps. In addition, the lights are switched on if any of the following faults occur:
^ The rain/light sensor detects a sensor fault
^ There is a fault in communication between the rain/light sensor and the light switch centre.

The following lights are controlled by the light switch centre:
^ If terminal R is ON, the side lights, the number plate light and the instrument panel lights are switched on.
^ If terminal 15 is ON, the dipped beam headlights are also switched on. If only the side lights are required at that setting, the switch on the light switch centre must be manually set to Side lights ON.
^ When the ignition switch is at position 0, the exterior/instrument panel lights are switched off.
The switching thresholds of the rain/light sensor can be set to 2 different levels using the Car Memory function.

Safety note:
Automatic control of the headlights is not a substitute for individual assessment of the light/visibility conditions (e.g. fog) by the driver. In order to avoid safety risks in such situations, the lights must be switched on manually by the driver.
The rain sensor controls the windscreen wiper interval in rain or snow.

Note: If the wiper switch is set to intermittent wipe, the activation condition is detected above a certain wiper frequency. When the vehicle leaves the factory, that wiper frequency is set to 15 wiper cycles per minute. The sensitivity of the rain sensor can be set to four different levels using the knurled adjuster on the wiper switch.