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

MODEL 164 up to Model Year 8

Shown on model 164.1

Fig 1: Identifying Rain/Light Sensor Component - Shown On Model 164.1

Courtesy of MERCEDES-BENZ USA

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.

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 (Fig 2), 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 (Fig 2), 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).

Fig 2: Rain Sensor Function Diagram

Courtesy of MERCEDES-BENZ USA

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).