This was most likely a problem with the electrical connection at the point where the pigtail is plugged into the power box. I put on a spare curled pigtail from my side box and it worked until I replaced with a new 15-ft straight pigtail and now that one isn't. When your trailer lights aren't working, your trailer is not working, and you are losing valuable time and money. To help trailer owners and enthusiasts, this article provides an. Save money on truck repairs by repurposing a damaged pigtail. Occasionally, you will see a big rig rolling down the road on which the lights don't all work.