Troubleshooting Trailer Running Lights Not Functioning When Connected to 2012 Ram 3500

Question:

In a previous thread of yours it was stated: We have seen this issue a few times and have seen some threads on the internet where people have had this problem and it was just a matter of replacing the fuse or in some cases the relay, but we have also seen situations where even after all of that was replaced the running lights still would not activate on the trailer. My question is: Which relay and where is it? Both J01 and J14 fuses are good, but I still dont accessory lights on my horse trailer. Thank you in advance.

asked by: Greg

Expert Reply:

Based on the question you asked this from, I assume you have a 2012 Ram 3500. Let's check for power on that pin at your 7-way trailer connection first. Use a circuit tester like # PTW2993 and check for power on the 11 o'clock pin when your trailer is not connected. If you have power there, then the problem is either in the connection between your truck and trailer or on the trailer. If you don't have power at that pin, then check the J14 fuse for your trailer running lights with the tester. You can put the probe on each side of the terminal to see if power is coming to the fuse and making it though the fuse. If you do have power coming and going from the fuse, then I recommend tracing that wire using a circuit tester every few feet to locate the short. You may want to run a new wire from that fuse block to your 7-way if you can't find the short using # 16-1-1 sold by the foot.

expert reply by: Jason S