Round 1 14 diameter metal connector allows 1 or 2 additional wiring and lighting functions such as back up lights auxiliary 12v power or electric brakes. Check with a test light or vom.

Industry Standard Wiring Configuration For The 4 Way Round
4 pin round trailer connector wiring diagram. We have the pollak heavy duty 4 pole round pin trailer wiring connector pk11402 that will accept up to 12 gauge wire. Trailer electrical connectors come in a variety of shapes and sizes. This is a trailer end plug. The vehicle side is the pollak heavy duty 4 pole round pin trailer wiring socket pk11404. Traditional trailer with brakes use a 5 pin connector. Color coding is not standard among all manufacturers.
6 way systems round plug. Refer to product instructions and locate wires on vehicle by function only. By law trailer lighting must be connected into the tow vehicles wiring system to provide trailer running lights turn signals and brake lights. It might be best to change to a 4 way of some type. The most common wire thickness for a trailer is 16 gauge but i bought thicker wiring for added durability. This type of connector is normally found on utvs atvs and trailers that do not have their own braking system.
Buy a 4 pin wiring kit with wires at least twenty feet in length so its long enough for your trailer. Depending on the size of your trailer and the number of lights you might want to check on the internet for the recommended gauge for your specific trailer. The black sometimes red 12v and blue electric brakes wire may need to be reversed to suit the trailer. Connecting the wrong color wires will result in mismatched taillight functions and confusion on the road. Below is the generic schematic of how the wiring goes. There are two types of 7.
7 way round trailer connector flat pin 7 way round vehicle connector flat pin 7 way round trailer connector round pin 7 way round vehicle connector round pin 7 way connectors aside from the three main lighting functions additional pins for electric brakes a 12 volt hot lead and backup lights are available. Blue electric brakes or hydraulic reverse disable see blue wire notes below in the trailer wiring diagram and connector application chart below use the first 5 pins and ignore the rest. 1 4 wire the first 4 pins white brown yellow green just like the 4 pin connector above. Do you have the correct wiring diagram for the round 4 wire connector. Looking at the front of the socket on the vehicle side with the cover raised the top left pole is the yellow left turnbrake pole the top right pole is the right turnbrake pole the. Above we have describes the main types of trailer wiring diagrams.
The basic purpose remains the same whether your truck and trailer is using a 4 way 5 way 6 way or 7 way connector. Use this 4 pin trailer wiring diagram to properly wire your 4 wire trailer plug. Most of the time the 4 way connector is wired as follows. Following the standard method for wiring a trailer connector is vital to the safety of your vehicle while towing. A 3 flat is indeed a tough plug to find. 4 pin trailer wiring diagram.
Note that this type of 4 pin connector is less common that 4 pin flat connector. Identify the wires on your vehicle and trailer by function only.