This tester has one side to connect the 7-pin plug of a trailer and another side to connect the 7-pin plug of a car very convenient.2. The ergonomic design of the 7 pin trailer plug will ensure its high performance work.3. This trailer tester can help you quickly check the fault of both vehicles circuit and trailers electrical system.4. Made of ABS plastic and copper, which is durable and you can use it for a long time for its long service life.5. Ideal in the commercial and private sector, for workshops, car and trailer rental, accessories trade, etc. Specification: Features: Main material: ABS and copperThe color blackItem type: diagnostic tools.Item name: trailer tester.Size: approx. 20*5*4cmBattery type: 9V (not included, you need additional purchase)Package size: 20 * 5.5 * 4.5cm / 7.9 * 2.2 * 1.8in Package weight: 194g / 6.8ozPackage List:K42161*7 Pin Trailer Test ToolOperation Guide:Trailer (can also be caravan or bike rack)Insert the plug into the tester connection.Press the yellow button on the side of the tester. If the wiring is good, all the LEDs light up. the function of each LED is (according to lso 1724): left indicator (yellow);2. fog light or 12V (blue);3. mass (white);4. right indicator (green);5. right rear light (brown);6. left brake light (red);7. left rear light (black). Attention : Pin 2 can be used either for a warning fog lamp or for a permanent 12V connection. If an LED does not light up, the corresponding wire is faulty. If all the LEDs do not light up, then the ground wire is damaged or all the bulbs are faulty.Car, motorhome 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. Repeat step 4 as before. You can also test the functions of each pin of the socket. Turn on the left turn signal (after turning on the ignition key).2. The corresponding LED should flash with the same frequency. If not, the left turn signal wiring is faulty/broken.3. Repeat steps 1 and 2 for the right turn signal, tail light, fog light and brake lights. With a +/- 4m extension cable, you can test the functions of the driver's seat more easily. Note: This product is European style, please confirm before ordering.