Rain Sensor: Description and Operation

GF54.21-P-6000RC Rain/light Sensor, Component Description
- with CODE (345) Rain sensor

Component Identification:

Location
The rain/light sensor is located on the inside of the windshield in the area of the inside rearview mirror unit (A67).

Task
Measuring light intensity and quantity of water on windshield. The rain/light sensor transmits the quantity of water on the windshield cyclically to the driver-side SAM control unit with fuse and relay module (N10/1).

Function principle of rain sensor
Infrared light is radiated from the infrared transmitter unit and led to the windshield. The intensity of the light reflected at the windshield is measured by the infrared receiver unit.

If the section of windshield around the rain/light sensor is dry, the light is almost completely reflected and the infrared receiver unit measures a high light intensity.

If the windshield is wet in the area of the rain/light sensor, 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.