Rain Sensing System

Rain Sensing System
The rain sensing system installed for some markets, provides automatic wiper operation when rain is detected on the windshield. The system detects differing levels of rainfall and varies wiper operation ranging from intermittent to maximum continuous, to suit prevailing requirements.

The system which is brought into operation by selecting AUTO on the wiper control switch bezel, does not preclude normal manual control of wiper operation.

The system consists of a rain sensor, an electronic control module and a dedicated wiper control switch.

The rain sensor is an optical transducer that is sensitive to changes in infra-red light penetration of the windshield created by the refractive effects of water droplets. The sensor elements consist of two groups of light emitting diodes which alternately project infra-red light onto the windshield and a photo-diode that receives resulting reflections from the glass. All of the infra-red light is reflected back from a moisture-free windshield, resulting in a constant 5V output signal from the sensor and no wiper activation. Rain falling on the light sensing area of the windshield results in refraction and diffusion of a proportion of the projected light with a corresponding imbalance of light received by the photodiode. This results in pulsed outputs from the sensor, the frequency and duration of which are directly proportional to the number and size of water droplets respectively. These pulses together with wiper switch position signals are received by the sensor control module and processed to mimic column switchgear operation. In this recognisable form, signals are input to the body processor module (BPM) where they are interpreted as normal wiper operation requests.







The rain sensor unit is installed on the inside of the windshield within the rear view mirror stem cover. The unit is secured to the glass by a special adhesive that facilitates service removal. When installing a rain sensor unit, it must be positioned in the clear circle within the obscuration band.







The rain sensor control module is a non-serviceable unit installed on the passenger side dash panel and connected to the rain sensor unit and the body processor module.







The column mounted wiper control stalk switch on vehicles with rain sensing installed, has an AUTO position (this replaces the first intermittent setting on non rain-sensing wiper controls), five intermittent settings, and normal, high speed and flick wipe positions.