8310 Wiper Blades

[dconine]

Does anyone know why the windshield wiper blades will not work when they are wet on a John Deere 8310? The wipers work when everything is dry, but as soon as water hits the windshield the wipers quit working. Dealer has looked at it and was not able to figure anything out. All electrical connections are clean & tight and there are no bare wires outside of the cab. Any input would be appreciated. Thanks...