When it comes to towing, one of the most important components is the wiring harness. A 7 pin wiring harness is commonly used to connect the towing vehicle to the trailer. It provides power to the trailer lights, brakes, and other electrical components. In this article, we will provide a comprehensive guide on the 7 pin wiring harness diagram.
What is a 7 Pin Wiring Harness?
A 7 pin wiring harness is a type of connector used to connect the towing vehicle to the trailer. It has seven pins, each of which has a specific function. The pins are numbered from 1 to 7, starting from the left side of the connector. The 7 pin wiring harness is commonly used to tow trailers, caravans, and boats.
The 7 pin wiring harness is designed to provide power to the following components:
| Pin Number | Function |
|---|---|
| 1 | Left-hand turn signal |
| 2 | Backup lamps |
| 3 | Ground |
| 4 | Right-hand turn signal |
| 5 | Electric brakes |
| 6 | Tail lamps |
| 7 | Auxiliary/12V power |
Pin 1: Left-hand turn signal
The left-hand turn signal pin is used to provide power to the left-hand turn signal lights on the trailer. This pin is typically wired to the left-hand turn signal wire on the towing vehicle.
It is important to note that some trailers may have separate turn signals for the left and right sides. In this case, the left-hand turn signal pin will only provide power to the left-hand turn signal lights on the trailer.
Pin 2: Backup lamps
The backup lamps pin is used to provide power to the backup lamps on the trailer. This pin is typically wired to the reverse light wire on the towing vehicle.
It is important to note that not all trailers have backup lamps. If your trailer does not have backup lamps, you can leave this pin unconnected.
Pin 3: Ground
The ground pin is used to provide a ground connection for the trailer. This pin is typically connected to the chassis of the towing vehicle or a dedicated ground wire.
It is important to ensure that the ground connection is secure and free from corrosion. A poor ground connection can cause issues with the trailer’s electrical system.
Pin 4: Right-hand turn signal
The right-hand turn signal pin is used to provide power to the right-hand turn signal lights on the trailer. This pin is typically wired to the right-hand turn signal wire on the towing vehicle.
It is important to note that some trailers may have separate turn signals for the left and right sides. In this case, the right-hand turn signal pin will only provide power to the right-hand turn signal lights on the trailer.
Pin 5: Electric brakes
The electric brakes pin is used to provide power to the trailer’s electric brakes. This pin is typically wired to the brake controller output wire on the towing vehicle.
It is important to ensure that the brake controller is properly installed and calibrated. Improper installation or calibration can cause issues with the trailer’s braking system.
Pin 6: Tail lamps
The tail lamps pin is used to provide power to the tail lights on the trailer. This pin is typically wired to the tail light wire on the towing vehicle.
It is important to note that some trailers may have separate brake lights and tail lights. In this case, the tail lamps pin will only provide power to the tail lights on the trailer.
Pin 7: Auxiliary/12V power
The auxiliary/12V power pin is used to provide power to accessories on the trailer, such as interior lights or a winch. This pin is typically wired to the battery or accessory wire on the towing vehicle.
It is important to ensure that the accessory circuit is properly fused and that the wiring is rated for the expected load. Overloading the accessory circuit can cause damage to the towing vehicle’s electrical system.
Wiring Diagram for a 7 Pin Wiring Harness
The following is a wiring diagram for a 7 pin wiring harness:
| Pin Number | Wire Color | Function |
|---|---|---|
| 1 | Yellow | Left-hand turn signal |
| 2 | Blue | Backup lamps |
| 3 | White | Ground |
| 4 | Green | Right-hand turn signal |
| 5 | Brown | Electric brakes |
| 6 | Red | Tail lamps |
| 7 | Black | Auxiliary/12V power |
FAQ
What size wire should I use for a 7 pin wiring harness?
The wire size for a 7 pin wiring harness will depend on the expected load. In general, a 12 gauge wire should be sufficient for most applications. However, if you are towing a heavy trailer or using accessories that draw a lot of power, you may need to use a larger wire size.
Can I use a 4 pin wiring harness instead of a 7 pin wiring harness?
While it is possible to use a 4 pin wiring harness instead of a 7 pin wiring harness, it will limit the functionality of the trailer. A 4 pin wiring harness only provides power to the left and right turn signals, tail lights, and brake lights. It does not provide power to the electric brakes, backup lamps, or auxiliary accessories.
Do I need a brake controller for a 7 pin wiring harness?
If your trailer has electric brakes, you will need a brake controller to provide power to the brakes. The brake controller is typically installed in the towing vehicle and is wired to the electric brakes pin on the 7 pin wiring harness.
What is the best way to test a 7 pin wiring harness?
The best way to test a 7 pin wiring harness is to use a multi-meter. First, check the continuity of each wire from the connector to the corresponding component on the trailer. Next, check the voltage output of the electric brakes and auxiliary/12V power pins. Make sure that the voltage output is within the expected range for the trailer’s electrical system.
Can I install a 7 pin wiring harness myself?
While it is possible to install a 7 pin wiring harness yourself, it is recommended that you have it installed by a professional. Improper installation can cause issues with the trailer’s electrical system and may lead to safety hazards on the road.
Conclusion
A 7 pin wiring harness is an essential component for towing trailers, caravans, and boats. Understanding the wiring diagram and function of each pin is important for proper installation and maintenance. By following the guidelines provided in this article, you can ensure a safe and reliable towing experience.
