Abstract: Testing apparatus is coupled to the plug used to connect the electrical system of a towed or trailer vehicle with a main or powered vehicle. The plug typically has terminals which connect related trailer vehicle electrical components with components in the main vehicle, e.g., the back up lights of the trailer vehicle are coupled to the back up lights (or transmission reverse gear) of the main vehicle. After coupling the testing apparatus to the plug portion attached to the trailer vehicle, switches can be used to activate selectively the trailer vehicle components. Instruments in the testing apparatus measure the electrical response to each activation and can be used to determine when the components are operating correctly. Similarly, when the portion of the plug coupled to the main vehicle is coupled to the testing apparatus, the response to activation of the main vehicle components can be monitored by the same instruments.

Abstract: A quick release mud flap hanger assembly for trucks and trailers comprises an L-shaped mud flap hanger having an elongate, outwardly projecting first leg and a shorter leg depending therefrom. A mud flap is suspended from the first hanger leg, and a hanger support bracket, adapted for mounting on a truck or trailer frame, has a guideway into which the second hanger leg is downwardly received. A resilient hanger portion, having a plurality of bends, each of less than 90.degree., interconnects the first and second legs, vibrational flexing of the first leg relative to the second leg being divided among such plural bends to reduce work hardening and greatly extend hanger life. Portions of a spring loaded detent element provided in the second leg project outwardly below portions of the guideway when the second leg is fully received into the guideway, to prevent accidental release of the second leg.