This Two-in-One Trailer Light Tester is Designed to Check if 12V Power from the Tow Vehicle is Reaching the Trailer's Tow Plug. This Tester also Indicates if the Vehicle's Tow Circuit is Properly Configured [TESTER BENEFITS] - This 7 Blade & 4 Pin Trailer Light Testers Allows You to Test for Taillights, Brake lights, Turn signals, Reverse lights, Electric brakes, and Auxiliary power [LED INDICATORS] - Includes 6 LED Lights Illuminate the Proper Functions of Vehicle-side Wiring Connector. Labeled on each LED (RT / BU / BK / 12V / LT / TM) [PRODUCTION PROCESS] - Moulded from ABS Plastic for Long-lasting use and Red LED Lights to be Bright and Legible. Pure Copper Contacts Make Good Electrical Conductivity [7 Blade 4 Flat Circuit Tester] - This Trailer Tester Can Also be Used as a 7 Way to 4 Way Trailer Adapter, Transfer the Power from Vehicle-side 7 Way Blade to Trailer-side 4 Pin Flat Adapter [FUNCTION CODES] - RT - Right Turn/Brake; BU - Back-up; BK - Electric Brakes; 12V - 12 volts (+); LT - Left Turn/Brake; TM - Taillights Trailer Circuit Tester; 4 Way and 7 Flat Pin; Tests Trailer Circuits Quickly and Easily on Most 12V Trucks and Campers

This circuit tester is a nice tool to have on hand to check the electrical connections between a tow vehicle and a trailer. Unlike ordinary separate 4-pin or 7-pin testers, this 2-in-1 design allows you to have both 4-pin and 7-pin testers, making it easier for you to use. Simply plug into vehicles tow plug and operate lights, brakes and turn signals to test circuits. When the socket is getting proper power, the tester's various LEDs will light up corresponding to each wire in the connector. Testing your vehicle-side socket is essential after installing a new custom vehicle-to-trailer wiring harness and is highly recommended every time you hitch up to tow.