Can I patch the trailer hitch tail light wire to the truck tail lights to circumvent whatever truck wiring harness problem is preventing my tail lights and reverse lights from working?
I cleaned up the rear light harness to frame ground connections. Test Light does not shine when connecting tail light wire to good ground.
If the fuse holds the additional current from the lights
Try each connection separately and see which of the lights come on. Use a piece of speaker wire to jack together and connect. Let us know if this works?
Do all the truck lights work before touching the trailer hook-up cable? If so, the lights that do not work, trace the wires to where they make a connection to the cable and make sure they are clean, good, and connected. Make sure the plug is wired correctly from the truck to the trailer. Brake lights to brake lights, running lights to running lights. It may be a defective plug, corrosion shorting connections, or lose or bad connectors. If you can, hook up another trailer or truck, and see if the lights do the same or if they work correctly. If the test light does not work, then find our why the power does not come to the plug. Start at the plug and work backwards to the last known working power source. As stated above, check fuses.