It does work

A few days ago it rained (I know, so what?). I noticed that my wipers were not wiping so good and thought maybe it's time to change them.
Today while driving I noticed some yellow spot on my wiper and wondered what kind of stain that was. Actually it's just the sensor that turned from black to yellow with a "Danger" triangle, obviously telling me that I have to change them.

I have to confess that I never really believed in those sensors that I supposed to tell you when to change your wipers, but it seems it does work. Maybe the previous times, I was just faster at changing them than was required.