Rain sensor system (optional)
The optional rain sensor system uses an
infrared sensor, located at the top of the
windshield in front of the rear view
mirror, to detect the presence of water
drops (or dirt) on the windshield. The
signal from the sensor is communicated
to the GM V, which activates the interval
wipe cycle if the wiper stalk switch
knurled knob (interval control) is in one
of the four interval settings.
The rain sensor functions by aiming a
beam of infrared light through the
windshield at a set angle. The beam is
reflected back and forth within the
windshield until it is detected by the
detector component of the rain sensor.
Rain drops (or other impurities) on the
outside of the windshield cause some of
the infrared to be dissipated outside the
windshield. As a result the detector
"sees" less infrared intensity. This is
interpreted as a need for the wiper to be
turned on.
System components:
An optical prism body attached to
the top of the windshield
Infrared emitter and detector diodes
Optics heater (to prevent
condensation from forming on
diodes and prism)
Wipers and Washers
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Summary of Contents for 1999-2005 M3
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