The wipers seem to have a mind of their own, and not necessarily consistent with what the rain is doing.
We refer to that setting as "Crazy Wipe"
Are they supposed to be fully automatic? Turning on by themselves when it rains? Ours does nothing when it rains till we override the auto setting for 1 wipe then put the switch back to auto, then it does the "crazy wipe" thing for the duration of the trip.