Rain/Light Sensor (If Equipped)
The rain/light sensor is located at the upper edge of the windshield, behind the rear view mirror trim panel. Contact between the rain/light sensor and windshield is provided through a silicon pad which is compressed during the assembly process by two locking retaining clips either side of the sensor.
The rain/light sensor unit attaches to the windshield through a retaining clamp, which latches onto formed tags on the windshield bracket.
The rain/light sensor contains a heater element. The software within the rain/light sensor uses the heater element to keep the optical unit clear of condensation. The software receives Ambient Air Temperature (AAT) signals from the Body Control Module/Gateway Module (BCM/GWM) assembly through the Local Interconnect Network (LIN) connection. Depending on the AAT signal value, the software activates the heater element.
The rain/light sensor send signals to the BCM/GWM assembly through a LIN bus connection for the optimum windshield wiper operation for the prevailing conditions to maintain the windshield in a clear condition at all times. The rain/light sensor is an optical unit, which operates on an infrared waveband. It uses the principle of the laws of reflection on interfacing surfaces between materials with differing refraction properties. The light is directed at an angle so that the light is reflected 100 % on the outside surface of the windshield and is transmitted back into the optical unit. To receive a 100 % reflection, the windshield surface must be clean and dry.
The light is reflected four times from when it leaves the transmitter diodes to when it is picked up by the receiver diodes. If the windshield is wet or dirty in the area of the optical unit, the clean conditions for 100 % reflection means that some of the light reflected is lost. As the windshield becomes dirtier or wetter, the received light is evaluated by the rain/light sensor and translated into a signal value. A micro-controller within the sensor monitors the change in signal and initiates the appropriate wipe cycle through LIN bus signals to the BCM/GWM assembly.
The software can compensate for the long-term effects of scratches and stone chips in the area of the optical unit and the short term effects of dirt or smears caused by worn wiper blades. A heater element is also contained within the rain/light sensor and uses ambient air temperature LIN bus signals from the BCM/GWM assembly to keep the optical unit clear of condensation.
The sensor receives a power supply from the BCM/GWM assembly. The 'Auto' wipers are activated when the wipers and washers control switch is moved to the 'Auto' position. The sensitivity of the rain/light sensor can be adjusted by rotating the windshield wiper intermittent switch on the wipers and washers control switch in a clockwise or counterclockwise direction. Clockwise rotation will increase sensitivity, while counterclockwise adjustment will decrease sensitivity. An increase in sensitivity adjustment results in a single wipe of the wiper motor.