Oyviny 3-in-1 Trailer Plug Tester – 4/5 Pin Flat & 7 Pin RV Light Tester with Dual-Sided LEDs

The Oyviny 3-in-1 Trailer Plug Tester is a compact, all-in-one tool designed for practical trailer wiring checks. It combines testing capabilities for 4-pin flat, 5-pin flat, and RV 7-pin blade connectors in a single, easy-to-use device. Its design emphasizes readability and quick diagnostics, making it a reliable addition to your roadside kit or shop setup. Important compatibility note: this tester does not work with vehicles equipped with lamp-out sensors, such as certain newer GMC, Chevrolet, BMW, VW, Audi, Mercedes-Benz, and Porsche models.

What you can test

• Tail lights, brake lights, and turn signals to confirm basic operation and timing
• Reverse lights to verify proper function when backing up
• Turn signal indicators to ensure proper sequencing and responsiveness
• Electric trailer brakes for structural control signals and responsiveness
• 12V auxiliary power to confirm available power on the trailer circuit
• Overall wiring integrity to help locate potential wiring issues quickly

Reading the indicators

• Dual-sided LEDs on both sides improve readability from multiple angles
• Each function has its own LED, making it easier to identify which circuit may need attention
• Green illumination provides a clear visual cue for successful function checks on site

Durable design and ease of use

Constructed from rugged ABS plastic with tin-plated copper terminals, the tester resists corrosion and provides stable conductivity. No batteries or extra wiring are required—simply plug in to test trailer circuits on trucks, boats, campers, caravans, and other towed configurations. The ergonomic design supports quick plugging and unplugging, helping you save time during roadside checks or maintenance sessions.

Note: For vehicles equipped with lamp-out sensors, this tester may not function as expected. Always verify compatibility with your specific vehicle model before testing.