Headlights on and wipers on, I think then they work, or you have to use the windshield washer with headlights on to get it to work.
Also Did you stop by enrique today?
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.