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

The Oyviny 3-in-1 Trailer Plug Tester is built to simplify trailer wiring checks across common connector styles. It combines 4-pin flat, 5-pin flat, and 7-pin RV blade testing in one compact tool, helping you verify circuits quickly before you hit the road. Designed for real-world use, it supports multiple trailer setups—from small utility trailers to larger campers—so you can troubleshoot with confidence.

Versatile testing for real-world setups

Whether you’re connecting to a car, boat trailer, or RV, this tester is ready to assist. The dual-sided LED indicators provide clear feedback from either side, making it easier to read readings in tight spaces or sunlit outdoors. The device itself requires no external power sources, and its straightforward plug-in design minimizes setup time when you’re in a hurry to secure a safe tow.

Compatibility note: Not suitable for vehicles with lamp-out sensors. If your vehicle includes this feature (for example some models from 2020 and newer), refer to the vehicle’s wiring guide before using a trailer tester to avoid false readings.

The tester is built to verify six essential trailer light functions, ensuring you can quickly identify miswiring or damaged circuits before you hit the road.

What it tests

• Tail lights
• Brake lights
• Reverse lights
• Turn signals
• Electric trailer brakes
• 12V auxiliary power

Design highlights and benefits

• Dual-sided LED indicators for easy reading from either side
• Durable ABS plastic housing that resists rust and corrosion
• Tin-plated copper terminals for reliable conductivity
• No batteries or wiring required; simple plug-in operation
• Ergonomic, compact design ideal for on-the-go use

In practice, this tester supports fast diagnostics on trucks, boats, trailers, campers, caravans, and other towed vehicles. Its clear LEDs help you quickly spot which wiring function is working and which needs attention, enabling you to plan repairs or rewire steps with clarity.

With its 3-in-1 capability, you can tackle 4-pin flat, 5-pin flat, and 7-pin RV blade connections in a single tool. The result is a versatile, portable tester that fits in a toolbox or glove compartment and reduces downtime during trailer maintenance or setup. While it simplifies many checks, always follow manufacturer guidance and local regulations when wiring or repairing trailer electrical systems.