Locating Third Brake Wiring
Locate third brake wiring after popping the hatch. Just follow the wire the way it runs through and locate its actual point. Also, check with the laws of your area if third brake light is allowed legally. In most areas third brake light is declared illegal and you can face legal difficulties if you wire the reel truck cap without knowing it.
Finding Positive Wire
Have your assistant to push the brake and you crawl underneath the truck to locate where the wiring runs. Have the assistant to push and release the brake pedal while you use a 12-bolt bulb to test each light. When the bulb goes on, it means you have found the positive wire. The light should be turned on while the pedal is pressed and should be off when the pedal is released.
Connecting With Wire
After locating the positive and right wire, run the wire through the shell from the truck bed down to third brake wire. Connect it with the red wire and use pliers to secure it, before wrapping a tape around it. Make sure you have secured the wire before taping it, and it is tightened enough that it does not separate with an easy push or pull.
Connect Black Wire
Find the black wire the way you have found the red one, in the harness and secure it with pliers. Attaching the black wire in the harness does your job, but make sure both wires are secured properly and cannot be removed easily. Also, tape around them so that they do not touch each other in the naked areas.