Ford Repair: wipers, locking nuts, wiper arms

Question
I have a 2000 Ford Ranger, extended cab.  My wipers stopped working.  The motor and switch are working. When the ignition is on, and the wiper control is on, I can hear the wiper motor running.  When I turn off the wipers, the motor stops, so I believe the switch and motor are good.  How can I make the wipers work, please?

Answer
if you can hear the wiper motor working then the problem is either the wiper arms lossened up from the wiper transmission or the wiper transmission broke. can you move the wipers by hand and do they move together ???? if so then they cam disconnected from the transmission. if the only moved individually then the locking nuts holding them in place came loose. they are 15mm nuts that are located at the end of the wiper arms