I reckon these are one of those "Why the **** do you need that" add ons.
I had them on my E Class Merc and they were a nightmare. Because it had auto wipers you didn't have the good old variable speed intermintant option. What that basically meant is that isf it was raining properly it was fine, if it was minor drizzle it was a pain in the backside.
I'm not being funny but how hard is it to flick the wipers on when you need them