Trailer Lights Only Work When Uncoupled from Hitch Ball

Question:

Hi. I’ve plugged my trailer into the vehicle 7 pin socket and all lights, side lights, brake lights work. When I I attach the trailer to the tow bar the side lights, indicators and rear lights of the trailer flicker then don’t work. Brake lights and indicators on the trailer wo K fine. Any suggestions pls? Thanks Vechile. Volvo XC90 r design year 2011. UK

asked by: Tony

Expert Reply:

The issue you described sounds like a ground issue which could be on the lighting assemblies, trailer side trailer connector, or vehicle side trailer connector. I recommend removing the ground wire on each of these and then sanding down the surface with some sandpaper and then using new mounting hardware to reattach the wires. The ground pin/wire inside the trailer connectors could also be loose as well.

Once you have performed the above please let me know if that fixes your problem and I would be glad to offer further assistance if not but regardless it boils down to just checking the wiring.

expert reply by: Conner L