Rain/Light Sensor
The rain/light sensor contains a number of transmitter and receiver diodes which emit and receive infrared light. By comparing the received light signal against the known transmitted light signal, the rain/light sensor can determine the amount of water on the outer surface of the windshield.
A = CLEAN AND DRY WINDSHIELD; B = WET AND DIRTY WINDSHIELD.
| ITEM | DESCRIPTION |
|---|---|
| 1 | Windshield outer surface |
| 2 | Optical element |
| 3 | Transmitter diodes (100 % light transmitted) |
| 4 | Rain/light sensor assembly |
| 5 | Receiver diodes (100 % light received) |
| 6 | Water droplets or water film |
| 7 | Receiver diodes (less than 100 % light received) |
| 8 | Lost light |
When the driver moves the wipers and washer control switch to the 'Auto' position, the BCM/GWM assembly detects a LIN bus message and monitors LIN bus messages received from the rain/light sensor. The rain/light sensor provides LIN bus messages with values ranging from zero to seven. A signal value of zero is interpreted by the BCM/GWM assembly as there being no water on the windshield.
A signal value from one to six is interpreted by the BCM/GWM assembly as there being a small amount of water hitting the windshield. In this instance, the BCM/GWM assembly initiates a slow wipe routine as detailed in the 'Windshield Wiper Slow Wipe' article above.
A signal value from seven is interpreted by the BCM/GWM assembly as there being a large amount of water hitting the windshield. In this instance, the BCM/GWM assembly initiates a fast wipe routine as detailed in the 'Windshield Wiper Fast Wipe' article above.
Rain/Light sensor sensitivity can be adjusted by turning the windshield wiper intermittent switch on the wipers and washers control switch to the required position. Six different sensitivity settings are available, which are broadcast over the LIN bus to the BCM/GWM assembly.
The software within the rain/light sensor can compensate the following:
- Short-term effects - For example dirt or smear, caused by worn wiper blades.
- Long-term effects - For example scratches or stone chips on the windshield, in the area of the optical unit.
When the self-adaptation is no longer possible, a recalibration routine must completed, using the Jaguar Land Rover (JLR) approved diagnostic equipment. The routine allows to reset the rain/light sensor values then the sensor can adopt to the new conditions. For additional information, Refer to: RAIN SENSOR