Rain/light sensor, component description - GF54.21-P-6000CW

MODEL 204.0/2 with CODE (345) Rain sensor up to Model Year 2008 

Illustrated on model 204.0 

Location 

The rain/light sensor is located on the inside of the windshield, in the area of the interior mirror.

Task 

To measure the light intensity and degree of wetting of the windshield Via the degree of wetting of the windshield the intermittent wipe of the wiper system (WSA) is controlled by two sensitivity stages. Various functions of the interior illumination (IBL) and exterior lights (ABL) are controlled automatically via the light intensity.

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 the light reflected at the windshield is measured by the infrared receiver unit (2).

If the windshield is dry in the area of the rain/light sensor (picture A), then the light is reflected almost completely and the infrared receiver unit measures a high light intensity

If the windshield is wetted in the area of the rain/light sensor (picture B), then part of the light is scattered from the windshield glass. As a result the intensity of the reflected light reduces and the infrared receiver unit measures a lower light intensity.

The light intensity measured by the infrared receiver unit represents a measure for the degree of wetting of the windshield. The smaller the measured light intensity the greater the degree of wetting of the windshield.

Via the overhead control panel control unit (N70) (with code (414) Power glass tilting/sliding sunroof) or the overhead control panel electronics (N70/3) (without code (414) Power glass tilting/sliding sunroof or with code (413) Panoramic glass sunroof with top sliding sunroof) via the wiper/inside rearview mirror LIN the information is looped through to the front SAM control unit with fuse and relay module (N10/1).