Running Lights Issue

[Lee & Sue]

We have a 2020 Ford F-350. Hadn’t had any issues until this.

[ScottandBobbi]

I just purchased a 2017 Grand Design Reflection 5th Wheel. While inspecting at the dealer the only running lights that worked were the front two one on each side Yellow, but they were very dim. Then they went out. The diagnosis was my truck fuse. I did not have extra fuses so I took the RV home over 2hrs away. I replaced the fuse and they two worked again and were dim. A few minutes later the fuse blew again. I have a 2016 Ram 3500 two vehicle. So I assume I have one of the above issues? Ill check tomorrow using the fuse method shown. Question does the end of the cord get warm to the touch? like luke warm? By cord I mean the umbilical cord that attaches to rv to the truck? I have a trip planned and payed for sites from Ohio to Texas and I leave the 10th of October so hopefully I can fix this issue. Suggestions appreciated. Ill know more tomorrow after the above listed test methods.

I should add that I also pulled a smaller rv with the same truck &pin and everything worked fine. The only issue is running lights the brake lights, 4 ways all work. If that helps.

[pnoetzel]

I just purchased a 2017 Grand Design Reflection 5th Wheel. While inspecting at the dealer the only running lights that worked were the front two one on each side Yellow, but they were very dim. Then they went out. The diagnosis was my truck fuse. I did not have extra fuses so I took the RV home over 2hrs away. I replaced the fuse and they two worked again and were dim. A few minutes later the fuse blew again. I have a 2016 Ram 3500 two vehicle. So I assume I have one of the above issues? Ill check tomorrow using the fuse method shown. Question does the end of the cord get warm to the touch? like luke warm? By cord I mean the umbilical cord that attaches to rv to the truck? I have a trip planned and payed for sites from Ohio to Texas and I leave the 10th of October so hopefully I can fix this issue. Suggestions appreciated. Ill know more tomorrow after the above listed test methods.

I should add that I also pulled a smaller rv with the same truck &pin and everything worked fine. The only issue is running lights the brake lights, 4 ways all work. If that helps.

I would pull the end of plug apart and see if the wires are tight on connection.
Should not be more than a small screw in the side , or an Allen head screws

[ScottandBobbi]

I assume I should do this for both the truck and the RV? I will keep you posted tommorow after I take a look and run some simple test from this post. Thanks everyone for the help also.

[ScottandBobbi]

Today I replace the OEM 7 Way on my Ram. I then used the fuse technique above to check the RV side of things. The fuse blew three times. The junction box has all the wires wrapped together in black tape.... i don't know wht to do now...do I rewire the box or do i start tracing wires to the running lights? Just to mention again, when I initially hook up the front left and right running lights come on but are very dim. Then after a while it blows my truck fuse. So Ill standby for any info.

[ScottandBobbi]

Here is the box after I took the black tape that was wrapped around it. I have ordered a new box and cable, already replaced my trucks 7 way. I hope this fixes it or I guess I have to take the bottom stuff off the RV and start tracing wires?

[jkwilson]

Here is the box after I took the black tape that was wrapped around it. I have ordered a new box and cable, already replaced my trucks 7 way. I hope this fixes it or I guess I have to take the bottom stuff off the RV and start tracing wires?

While not impossible changing the cable will fix it, it’s a long shot. You can easily determine if the cable is the problem by unhooking the running light connection at the box and seeing if the fuse still blows. If there are multiple wires running out of the box to running/tail lights, reconnect them one at a time and see what lights work and when the fuse blows.

[ScottandBobbi]

Thank you for the info. I figured replacing the truck 7 point and then the bow and cable would at least eliminate any issue that might be their. When i used the methods mentioned in this thread with the fuse it blew. I tried it three times and it blew the fuse every time. I assume I am going to need to take the bottom foam or whatever from the entire bottom of the RV to trace wires? Sigh.

Its odd that when hooking it up the two front running lights although very dim work, until the fuse blows on the truck. I disconnect The truck and used the fuse method to test the rv side and it pops the fuse every time. I'm pretty sure their is a short to something beyond The front two running lights...but I wont know until I trace wires or test each one. I'm new to all this so past this point things will be hard for me to understand.

[pnoetzel]

Thank you for the info. I figured replacing the truck 7 point and then the bow and cable would at least eliminate any issue that might be their. When i used the methods mentioned in this thread with the fuse it blew. I tried it three times and it blew the fuse every time. I assume I am going to need to take the bottom foam or whatever from the entire bottom of the RV to trace wires? Sigh.

How about taking individual bulbs out of the trailer light sockets, maybe eliminate the bad one that way?

[ScottandBobbi]

The only running lights that come on are the front two one on each side, and both are dim. I've put new bulbs in all of them and still only the front two until the pop the fuse.

I do see what your saying but if they are not on how could i tell? I just dread taking the bottom off the rv, but it seems like im going to have to at any rate?

Ill try tomorrow Ill need to get a ladder and my wife to help pull them before the fuse pops.