LR3/Disco 3
The rain/light sensor contains transmitter and receiver diodes, which transmit and receive infrared light, which is directed
onto the windscreen via an optical unit. The light is directed at an angle so that the light is reflected 100% on the outside
surface of the screen and is transmitted back into the optical unit. To receive a 100% reflection, the outer screen surface
must be clean and dry.
The rain/light sensor is active when the wiper column control switch is in the intermittent position. The rain/light sensor
suspends wiper operation when the area of the windscreen for the rain/light sensor is dry and operates the wipers
continuously when the windscreen is subject to heavy rainfall.
The sensitivity of the rain/light sensor can be adjusted by the driver using the intermittent rotary switch on the wiper stalk.
Six sensitivity levels of the sensor can be selected, which has the effect of increasing or decreasing the wiper delay
period, allow driver adjustment for the prevailing conditions. When several continuous wipe cycles have taken place, the
sensor will maintain the continuous operation to avoid switching back to intermittent from a continuous wipe and back
again.
The rain/light sensor receives vehicle speed information from the Anti-lock Braking System (ABS) module on the Local
Interconnect Network (LIN) bus via the CJB. The sensor increases the sensitivity as the speed increases to optimise
wiper operation. When the vehicle speed is reduced to less than 5 mph (8 km/h), the sensitivity is automatically reduced.
Below this speed the wipers will only operate continuously in very heavy rain.
Automatic Headlamp Operation
A light sensor is incorporated in the housing of the rain/light sensor to control the operation of the automatic headlamps.
The automatic headlamps will function when the lighting control switch is in the 'AUTO' position and the CJB receives a
lights on signal from the rain/light sensor. For additional information, refer to
Exterior Lighting
(417-01 )
WIPER CONTROL COLUMN SWITCH
3
Transmitter diodes (100% light transmitted)
4
Rain/Light sensor unit
5
Receiver diodes (100% received)
6
Water droplets/film
7
Receiver diodes (less than 100% light received)
8
Lost light
Item Part Number
Description
1
Wash/wipe control column switch
2
Intermittent variable delay rotary control
3
Intermittent/continuous rear wipe
4
Rear wash position
5
Fast speed wipe position
6
Normal speed wipe position
7
Intermittent/rain sensor wipe position
