Trailer lights go out while towing

[Steuber]

I have replaced the 7 pin plug and cord making all connections with heat shrink butt connectors and heat shrink tubing. Checked all exterior lights by removing and checking wires and connections. While hooked up and sitting the lights are solid. Once I drive it's anywhere from 5 minutes to an hour or longer to blow my running lights fuse in my truck. After this the only lights that work are the left brake and turn. All other lights are out. Trailer brake still functions properly. Any ideas? Im so lost with this and really can't afford the massive potential cost. Thank you for any help. 2017 jayflight slx 264bhs. If there is some way to use the trailer brake still but use emergency magnetic lights that'd be great too if I can't solve this issue. I gave a big move fir my family in just under two months.

[mrmom]

Just guessing based on past experience, but since you have replaced the plug and wiring on the trailer, I think I would check the receptacle on the TV. Sounds like you have an intermittent short somewhere.

One other thing that comes to mind is that after the fuse blows, you only have left side stop/turn light. Does that mean you are blowing 2 fuses or only the running light fuse?
If blowing 2 fuses, that would lead me to believe that the short is in the circuit to the right side taillight. If the short was in the wiring inside the trailer, you would probably only blow a fuse for either the right stop/turn or the running lights, not both.

[Steuber]

I am blowing the running lights fuse 20amp and the right turn light fuse. I am going to disconnect in the junction box the right lighting wire and see if that stops it from shorting out.

[2edgesword]

Sounds like an intermittent short somewhere along the wiring that gets trigger during vibration while traveling.

[ALJO]

First you test all the functions on the TV receptible, if all correct the problem lies at the RV
You then check each connection at the TT plug to isolate which circuit is at fault.

[mrmom]

I'm guessing that you still have the 4" square metal box on the trailer tongue where all the wiring meets. I replace mine with one of these Electrical Trailer Junction Boxes. So much easier to keep everything organized and neat. Makes troubleshooting easier as well.
https://smile.amazon.com/s?k=electri...f=nb_sb_noss_1

[RogerR]

I would pull the cover off every running light starting with the right brake. I bet either the socket is bad on one of the lights or the wiring is shorting where it comes through the hole in the outside wall into the brake light or running light.

I changed out to Led tail lights and they just drilled a hole in the metal and pulled the wires through. The wiring litteraly rested on the metal edge of the trailer skin. Needless to say, I fixed them and my next project will be to go over the running lights to replace with LED and fix this poor, cheapo, practice of Jayco.

[Steuber]

Yea I did take all including the rear brake light off and check the wiring. I think im going to go through them again. I plan to disconnect wires from the lighting one by one and drive around to single out which one it is. If that isn't somehow fruitful then I don't know what to do with my big move coming up across country with the family. Emergency lights doesn't work since I would lose trailer brake function. I don't have time for a repair shop to take potentially a couple months on it.

[ALJO]

Sometimes a good technical neighbor might give you an hand, two thinkers is better than one. Even a bulb during travel can short to ground and blow a fuse.

[curver900]

if you can't find the short.. just run new wire to the tail light and blinker... sometimes it is easier to just replace it...where ever it is shorting out should be an easy find.. blowing a 20amp fuse should produce some easy to view eye candy... if nothing else get under it and move the wires one at a time with a helper to tell you when the fuse goes poof...

[Steuber]

I wanted to do that but the underbelly seems to be solidly sealed shut with the cover they put on it. It didn't seem to budge at all really. I thought about running new wire but didn't seem possible without wrecking my trailer to find a chaffed wire.