Rain/Light Sensor With Additional Functions, Component Description - GF54.21-S-6005TRA

Model 447 

With Code JF1 (rain sensor) 

Model 448.8 

With Code JF1 (rain sensor) 

Shown on humidity sensor/light sensor/rain sensor/sun sensor (B38/3) 

Location 

The humidity sensor/light sensor/rain sensor/sun sensor (B38/3) or the rain and light sensor with additional functions (B38/5) is located under the trim of the overhead control panel (OCP) control unit (N70). This panel is in the headliner in the center between the driver and front passenger seat.

Task 

The humidity sensor/light sensor/rain sensor/sun sensor (B38/3) or the rain and light sensor with additional functions (B38/5) has the following tasks:

• Reading in of signals
• Recording states
• Sending signals

Reading in of signals 

The humidity sensor/light sensor/rain sensor/sun sensor (B38/3) or the rain and light sensor with additional functions (B38/5) also reads in the following signals from the signal acquisition and actuation module (SAM) control unit (N10/1) via roof LIN (LIN B13):

• Activation and sensitivity of sensor
• Outside temperature
• Vehicle speed

Recording states 

The humidity sensor/light sensor/rain sensor/sun sensor (B38/3) or the rain and light sensor with additional functions (B38/5) records the following conditions in the area of the windshield:

• Background light intensity via the light sensor
• Degree of wetting over rain sensor
• Air humidity on the inside of the front window via the humidity sensor
• Intensity of solar radiation via the sun sensor

Background light intensity via the light sensor 

The background light intensity and the brightness of the road in the viewing direction are determined by the light sensor.

Degree of wetting over rain sensor 

The degree of wetting of the windshield is determined by the rain sensor using a transceiver distance. An infrared transmitter unit beams infrared light at a defined angle to the interior of the windshield, which is almost completely reflected onto an infrared receiver when the windshield is dry.

If there are water droplets 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 is weakened. The lower the measured light intensity the higher the degree of wetting of the windshield.

Air humidity on the inside of the front window via the humidity sensor 

The humidity sensor measures the relative humidity directly on the inside of the front window and uses it to determine the dew point temperature.

Intensity of solar radiation via the sun sensor 

The interior temperature and the blower output are adapted according to the intensity of the solar radiation on the vehicle. In the event of one-sided solar radiation, an adequate temperature difference is set between the left and the right regulated specified temperatures.

Sending signals 

The humidity sensor/light sensor/rain sensor/sun sensor (B38/3) or the rain and light sensor with additional functions (B38/5) sends the following signals to the signal acquisition and actuation module (SAM) control unit via the roof LIN:

• Requirements for exterior lights
• Background light intensity
• Solar radiation
• Degree of windshield wetting for the windshield wipers
• Air humidity on inside of windshield

	Overview of exterior lights system components	Model 447 with code JF1 (rain sensor) except code XM0 (Facelift) Model 448.8 with code JF1 (rain sensor)	GF82.10-S-9998TRA
		Model 447 with code JF1 (rain sensor) with code XM0 (Facelift) except code XM7 (MOPF II)	GF82.10-S-9998TRF