I have a brand new 2017 Grand Cherokee (< 1000km) equipped with rain sensing wipers. I have enabled the rain sensing feature via the touch screen setting. As I understand it, the control stalk positions for interval wiper operation (when rain sensing is disabled) function as sensitivity settings for rain sensing when the feature is enabled, with the position for longest delay corresponding to least sensitive and shortest delay for most sensitive.
I am finding that with rain sensing operation activated as I understand its use, at any setting, the wipers rarely wipe; so much water has to accumulate on the glass before a wipe that it's difficult to see out. When I turn off the rain sense feature, the wipers work exactly as expected for an interval wiper system, so I know the issue resides with the rain sensing feature and not with any other part of the wiper system.
Before purchasing my car, I drove a 2016 Grand Cherokee rental. I had no idea it was equipped with rain sensing wipers and that they were enabled, only realizing this as I was driving in rain and found them to work extremely well. They worked so well, I decided it was a "must have" feature on the car I eventually bought.
What could account for the less than satisfactory performance of the wipers on my own car? I know how the technology works (measurement of internal reflections of an infrared beam via a device attached to the glass behind the rear view mirror). I know that treatments like Rain-X adversely affect the performance of rain sensing wipers; I haven't applied any, and I see no indication any was done by the dealership.
What I'd like to understand is what factors could affect the operation of the rain sensing - how it decides what "clear" is like and what could affect, control, or "re-set" that threshold, and whether a service visit could accomplish anything.