1: If the trailer has the 5pin plug the 5th or blue wire should light the back up light as well as open the valve in the Master Cylinder… 2: Also there is a cut out on the side of the tounge in an oval where a key fits that will stop the cylinder from compressing.. info should be in manual…Cpt.Gary Harlan (Harlo) USCG Liscd Fishing Guide Tishomingo, MS Roger Stegalls Professional Guide Service Sponsors: BassCat (of course!), Strike King, Falcon Graphite Rods, Gary Yammamoto Custom Baits