I am at my wits end! My running lights went out half way home one night! I did test all my fuses and they are ok, tested pig tail and that seems good so my guess it is the trailer? I have electric brakes on the trailer. My turn signals work and I have tail lights just no marker lights! And the brakes lock up when I back up so I have this tool to put in the trailer to release the brakes. I think it is a Marine Master trailer! Any help would be great?