The ground point is at the steering column. You need to remove the two plastic covers. The right side switch has a ground wire from switch to the screw. If the screw is loose the wipers will not shut off. Under the front vent panel is where the wiper motor resides and there is a ground wire to the cowl sheet metal. That ground can become loose as well, but usually keeps the motor from running at all. Hope this helps. Pauli