Ambient Light Sensor: Description and Operation

GF54.21-P-6000GZ Rain/light sensor, component description
- 164 up to model year 8

Component Identification:

Location
The rain/light sensor is located on the inside of the windshield under the inside rearview mirror.

Task
Measuring light intensity and quantity of water on windshield.

Component Identification:

Function principle of rain sensor
Infrared light is beamed from the infrared transmitter unit (1) and is directed to the windshield (3). The intensity of light reflected at the windshield (3) is measured by the IR-receiver unit (2)
If the windshield (3) is dry in the area of the rain/light sensor (picture A), then the light is almost completely reflected and the IR-receiver unit (2) measures a high light intensity.

If the windshield (3) is wet in the area of the rain/light sensor (picture B), then part of the light is scattered out of the glass of the windshield (3). As a result the intensity of the reflected light reduces and the IR-receiver unit (2) measures a lower light intensity.

The light intensity measured by the IR receiver unit (2) is a dimension for the quantity of water on the windshield (3). The lower the measured light intensity the greater the amount of water on the windshield (3).

Function principle of light sensor
The rain/light sensor measures the outside light intensity.

The information is transmitted to CAN class B by the overhead control panel control unit (N70).