Why are only my running lights working on my trailer?
Why are only my running lights working on my trailer? Turn Signals on Trailer Not Working When Running Lights are On The most likely cause for the turn signals not to work when the running lights are on with your trailer is a bad or weak ground. It's very possible that a weak ground connection can be just strong enough to allow sufficient current for some… How do running lights work on trailer? How Your Trailer Lights Work. Trailer wiring consists of a plug connected to the tow vehicle's lighting circuitry, a matching connector on the trailer, a wiring harness...