Trailer Wiring Diagram – Lights, Brakes, Routing, Wires Some places label the 5th pin for “Reverse Lights”. Certainly that works, but make sure to note it on the trailer because Blue is the color for brakes. Also, some trailers with hydraulic brakes use this 5th pin to disable the brakes when the vehicle is reversing. This is not shown in the trailer wiring diagram above. Wiring LEDs Correctly: Series & Parallel Circuits Explained Hopefully those looking for practical information on electrical circuits and wiring LED components found this guide first. It’s likely though, you’ve already read the Wikipedia page about Series and parallel circuits here, maybe a few other Google search results on the subject and are still unclear or wanting more specific information as it pertains to LEDs. Led Light Bar Wiring Diagram | Free Wiring Diagram Assortment of led light bar wiring diagram. A wiring diagram is a streamlined standard photographic depiction of an electric circuit. It reveals the elements of the circuit as streamlined forms, and also the power and also signal connections between the tools.