1997 Mercury Mountaineer Windshieldwiper

The "Park Switch" goes bad on these wiper motors sometimes. If that's the case you'll have to replace the wiper motor/transmission.

But, before replacing anything, check the windshield wiper relays (2). If one is sticking closed the wipers will stay on. If the relays check out OK, then the motor/transmission is your next option.

** To check the relay(s), simply switch one with another identical relay from somewhere else in the fuse box, then see if the wipers operate properly. If so, the relay is bad.