Features: 1.Trailer tester for 7-pin plug and socket connection. 2.Used to test whether the trailer power supply wiring is normal. 3.With 6 LED indicators for easy observation. 4.Clearly show any faults in your wiring on your car or trailer. 5.Lightweight and portable, easy to operate, worthy of your trust. Specification: Condition: 100% Brand New Item Type: Socket Connection Tester Color: Shown as Picture Material: ABS+ Copper How to test the connection of a Trailer (can also be a caravan or bicycle carrier) 1. Put the plug in the connection of the tester. 2. Press the yellow button on the side of the tester. 3. If the wiring is good, all the LEDs light up. the function of each LED is (acc iso 1724): A. Left Hand Indicator (yellow) B. Fog Light or 12v (blue) C. Mass (white) D. Right Hand Indicator (for Green) E. Right Rear Light (brown) F. Left Brake Light (red) Left Rear Light (black) Note: 1. Put the tester in the socket of the car. 2. Press the yellow button on the side of the tester. 3. If the wiring is good, all the LEDs light up. Do again steps 4 as previous. You can also test the functions of each pin of the socket. 1. Switch on the left hand indicator (after switching on the ignition key). 2. The corresponding LED must flash with the same frequency. If not, left hand indicator wiring is defective/broken. 3. Repeat steps 1 and 2 for the right hand indicator, rear light, fog light and stoplights. 4. The pin 2 can be used either for a warning fog lamp or a permanent 12V connection. 5. If a LED doesn't light up, it is because the corresponding wire is defective. If all the LEDs don't light up.