Rain Sensor: Description and Operation

GF54.21-P-6000RI Rain/light Sensor, Component Description

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
The rain/light sensor records the current ambient light intensity and the degree of wetting of the windshield. It uses this information to generate a corresponding signal which is needed to control the following functions:
- Intermittent wipe of wiper system (WSA)
- Interior illumination (IBL)
- Exterior lights [ABL]

Design
The rain/light sensor is a combined optical sensor.

Function
The light intensity of the vehicle's surroundings is measured via an ambient light sensor.

The level of wetting on the windshield is determined using a transmission/reception path. An infrared transmitter unit emits infrared light at a defined angle on the inside of the windshield which, in the case of a dry windshield, is reflected almost completely to an infrared receiver unit. If water droplets are located on the outer surface of the windshield, a considerable part of the light is diverted. The intensity of the reflected light is correspondingly lower and the reception signal of the infrared-receiver unit is weakened. The lower the intensity of reflected light measured, the wetter the windshield.
The signals from the rain/light sensor are read in by the overhead control panel control unit (N70).