Both auto rain wipers and sunroof/window closing works off of the RLS Rain Sensors. As others mentioned, its always a hit or miss thing., has to some something with the Sensor itself.
One thing i noticed was, ever since i replaced my windshields (stock windshield broked) replaced with a OEM equivalent one, which doesnt have the light green tint as the original glass.
Replacement Glass seems to work better with the RLS., the sensing is more responsive and works better now.
Thinking that there should be a VCDS setting to adjust the sensor threshold.
Last week, I took my newly acquired VCDS and attempted to enable the rain sensor. Our car is one of the '13 Passat SELs that has the sensor behind the mirror. Although I ran through the procedure three times in VCDS, the check boxes were always set back to the original settings, so I assumed it was blocked at some level deeper than VCDS can access, and activating the rain sensor was a no-go.
Imagine my surprise yesterday, as we drove home in rain, when I turned on the intermittent wipers and the rain-sensing system started working. It's not quite what I expected. Evidently if the rain is light enough, the intermittent wipers just keep going on whatever the setting is on the stalk. Then, as the rain / speed (and perhaps some combination of those, I'm not sure) increases, the wipers move to a "Speed1" setting identical to the first wiper setting beyond intermittent (the second detent up). Then, when the rain gets really hard (I had the cruise set to 65) it jumped up to "Speed 2," as far as I could tell, identical to the highest (uppermost) speed setting on the wiper stalk.
As the rain abated, the speed would slow down. At one point, we were out of the rain band altogether, and it stopped, even though the stalk was still on the "intermittent" setting.
So— I've got rain sensing wipers of some kind....whether it was what was intended is questionable, as there are all kinds of stories about how this "feature" behaves.
