You are playing the arcade mode right? we added the automatic turning on and off of the wipers in this mode. If you don't want it, please choose the realistic mode.
What do you mean by steering wheel? Your own wheel or the in-game wheel? The in-game wheel doesn't have a wiper function and it will not in the future. We tested all our busses, and yes, the Scania has a little problem which we are trying to fix but we couldn't detect something in the other models.