Its the headlight washer. It sprays heated liquid on to the head lights in cold weather. If the car is standing still and you press the button inside it will actually shoot up onto the hood/bonnet......at least mine does and my friend would press it right after me getting the car washed just to piss me off....lol
I thought they were utterly worthless on my 2000 SLK so I didn't get them on my 32. Much cleaner bumper without them and yes they shoot to the roof if you hit them by accident. I just had no need for them.
They useless for the warmer climates. In northern Europe they are very useful when combined with that pungent alcohol based fluid in clearing ice. I thought they were a gimick too until I had to use it on a German Christmas trip.
Ok, here's the scenerio...I spend an hour washing the exterior, being very careful to flip my wash glove and carefully dry it off as well...then I move to the inside and as I'm putting the F2000 on the center console, I invariably hit that Fricken button and pour washer solution not just on the headlights and roof but all over the hood and both front fenders as well!! I've done it more than once (hmm, that would make me an idiot<lol>). It's true, looks cool at the dealer when someone else shows it to you but I've never driven in mud where I actually needed headlight washers...not even in my Expedition!
Well, I don't know if the washers are different between the R170 and R171... but I can report that the R171 washers actually work quite well to remove bugs from the headlamps -- no wiping, just very high pressure. I used them a few times on a long drive to Las Vegas (abt 1200 miles roundtrip). I can understand how annoying it is to trigger them at a standstill, but I don't recall they can be triggered unless the car is running... at least not in the 171...
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