Rain sense wipers ? ?

Am wondering where/how the wiper rain sensors on my '08 Lucerne are located and how they 'sense'. At a stop, they don't really seem to work all that well. Window is pretty well completely
covered and they don't come on. While moving, they do a better job, for the most part, speed up as the rain becomes heavier. However a passing vehicle with the large 'mist spray' doesn't seem to activate them very well. Thx Zork
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This is likely the one GM uses:
http://www.trw.com/images/rain_sensor.pdf
Steve
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Around the rear view mirror you will see a sort of screen on the windshield; that is the sensor.
By adjusting the timing of the intermittent wipers you change the reaction to the sensor. One the lowest speed it does not react very well. One notch up is a big improvement under the most adverse and changing conditions.
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When the car is moving the windshield collects rain water faster because you're moving into the water. That's why you notice less wiper activity while the car is stationary.
Have you tried increasing the sensitivity by rotating the knob on the turn signal lever? Each detent on the lever will make the wiper more sensitive to the amount of water on the windshield.
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Bishoop wrote:

but a darn good system.
Remember too that when you are using rain sense and after it activates, your headlights will be controlled by Rain Sense (this meets some state law requirements), not by the day-night sensor or the /Twilight/ timer. So, they may stay on until the kill function in the Battery saver shuts them down.
Good scheme is to always shut off the wipers as you pull into the garage.
-- pj
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