Quickly and easily test trailer circuits on most light to medium duty trucks and campers. Tests vehicle circuits on 7 Flat/Spade Pin connections - quickly identifies faulty circuits. Made from LEDs and ABS plastic - ensures durability. 1 Year Limited Warranty Tester plugs into vehicle side wiring harness. Each of the 7 LEDs on the tester correspond to the correct circuit. An LED not lighting up for a particular circuit indicates a problem from the vehicle wiring harness back to the fuse box.