Troubleshooting Trailer Running Lights Not Working on Trailer

Question

Question:

Hi, I was having an issue with my marker lights on my landscape trailer and i order the following parts on order 103920953 and installed them on the trailer side to help determine the problem stop with the use of the LED lights. I first found that they self piercing pins didnt penetrate the plastic cover. So I squeezed the teeth a little tighter and was able to get a good connection. I had it working and then realized that they trailer had 2 wires going into the one pin. I simply combined the wires together with a butt connector and used heatshrink tube to seal it off. I thought that i had it working and then i went o take it out today and the marker lights we not working. I happen to look at the vehicle tail light and noticed that the bulb was out and i replaced the bulb and i thought that would do it. Once i plugged the tailer wire back in the light didnt turn on. Im so confused and since it is so freaking cold here in Connecticut and I dont have a place to pull it in out of the cold it sucks trying to trouble shoot the issue. I was hoping that you could provide so insight to the problem. Is it the combining of the brown wires? Could it have always been a ground issue?

asked by: Craig

0

Expert Reply:

I checked your order notes and it looks like you ordered part numbers # 9653P, # HM48192, and # HM48190.

It could be as simple as a bad ground that is causing the running lights to now work, but since the bulb was blown that would more indicate a short on the wiring of the circuit somewhere. Check the wiring of the circuit for any exposed or cut wire and fix as necessary. I realize that's the last thing anyone wants to do in the cold but that is most likely the problem. The way you have the running light circuit would not be a problem either. Most trailers have to do what you ended up doing by running the two wires together.

If that doesn't solve the problem here is what we recommend most people for tracking down trailer wiring circuits that don't want to work:

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.

If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue.

Make sure that the trailer side connector are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

If the problem is on the vehicle side then I would first recommend you double check how the harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well.