How to Repair a Bad Tail Light Wireby K.K. Lowell
When a vehicle tail light does not work even though you have replaced the bulb, you may have a bad tail light wire. The first step in knowing how to repair a bad tail light wire is verifying that a problem exists. From there move on to diagnosis, which will tell you what, and where, the problem is. The final step is the repair of the problem.
Turn on the parking lights and verify that only one tail light is not working. If both tail lights and the license plate light aren't illuminated, check the vehicle fuses.
Remove the lens from the tail light that is not working. Then remove the bulb and replace with a known good bulb. If the bulb does not light, remove it and probe the socket with the test light or multimeter to check for power. If power is found in the socket, the problem is a bad ground wire or connection. If no power is found, the wire must be visually inspected and probed along its length until power is found.
Disconnect the first tail light wiring harness connection and probe the car side for power. Finding power here indicates the problem is in the wire between this connector and the socket. Plug the connector back in and probe the wire every few inches until no power is found.
Probe backwards along the wire until power is found again. Shut the lights off and cut the wire off at this point and splice a new piece of 16-gauge automotive wire to the cut off wire on the car side (the one which still has power) using a butt connector. Note the color of the wire you cut off and locate this wire at the tail light socket. Cut the wire off, leaving enough wire still connected to the socket to splice onto the new 16 gauge wire using another butt connector.
Tape the connections very securely. This will help prevent corrosion which will reduce the voltage to the light.
Turn the parking lights back on the test the repair.