Range Rover Wipers and Washers: Rain Sensor Description
WIPERS AND WASHERS
DESCRIPTION AND OPERATION
84-13
The rain sensor unit attaches to the optical unit via four clips which latch onto formed tags on the optical unit. Positive
retention is achieved by two retaining clips which force the clips onto the tags. The retaining clips must be withdrawn
to facilitate sensor removal.
The sensor provides information to the BCU, via the K bus, for the optimum wiper operation for the prevailing
conditions to maintain the screen in a clear condition at all times. The rain sensor is an optical unit which operates on
an infrared waveband. The sensor uses the principle of the laws of reflection on interfacing surfaces between
materials with differing refraction indices.
Rain Sensor Functionality
A. = Clean and dry windscreen; B. = Wet and dirty windscreen
1 Windscreen - Outside surface
2 Optical unit
3 Transmitter diodes (100% light transmitted)
4 Rain sensor unit
5 Receiver diodes (100% received)
6 Water droplets/film
7 Receiver diodes (less than 100% light
received)
8 Lost light
The rain 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.
M84 0421
1
5
A
4
3
2
4
6
1
3
2
8
7
B