Yesterday with strong intermittent rain I had the opportunity to check that ... (blue box)
...being pleasantly surprised at how well it works.

(Comfort and safety at the same time)
wanderlust
Another good reason to make electrical installations (wirings) with
original equipment in the right way. (BCM
Max 
)
There are countless other reasons ...
In perfect combination
with ...
...this way the wiper speed depends on the amount of rain on rain sensor. Works continually but varying the wiper speed automatically and it stops when its function is not required.
If you do not have rain sensor (or you have rain sensor but not have Byte14 Bit7 marked) the switch function (A) is not automatic, its function is to modify
the delay between intervals of sweep wiper manually.