On mine...
OFF is off--no matter how much water (i.e. car wash)
I position is self-sensing intermittent--initial wipe, then as needed
II position is low speed constant
III position is high speed constant
Light push-in on end of stalk is single swipe, heavier push-in is washer.

My system has 2 relays--Wiper On/Off and Wiper I/II. Don't know how the electricity works, but IF you have the sensor spot on the windshield but no variable speed, one of the relays may be out. They're about $5-$6 on fast lane, and it's a relay that fits multiple locations.

We're at 2 above here this morning--all the water is solid. Good luck.

__________________
Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)