Tail lights and blinkers not working.

[the Gilly's]

Tail lights and side marker lights and blinkers stopped working. Worked good last week when we brought it home for the first time. I have power to said lights behind the 2 batteries in the battery bay. Up to where the wires go into the underbelly. Any idea what or where to check next?

 

[BryanValRox]

Tail lights and side marker lights and blinkers stopped working. Worked good last week when we brought it home for the first time. I have power to said lights behind the 2 batteries in the battery bay. Up to where the wires go into the underbelly. Any idea what or where to check next?

Are there any more specifics you can supply?
Is it all tail lights? Is it all Marker Lights? Is it all Blinkers?

 

[the Gilly's]

Yes. All the tail lights are not working And just the upper marker lights work. No side marker lights or blinkers work. I have power to all lights to as far as I can reach in the battery bay.

 

[BryanValRox]

Good morning,
Thanks for the update.
Generally, I would start by ensuring that trucks light plug is functioning as expected. They make inexpensive plug in testers that give you visual confirmation that each circuit is working as expected. Once that is confirmed, I would visually inspect the trailer cord plug to ensure there are no spread open pins or bent over terminals. After that, I would move to the trailer 7 pin junction box. I would be inspecting for loose connections or broken wires, both on the power side of the circuit and the ground side of the circuit.
If all checks out on the power and ground sides, then it becomes a matter of tracing the circuit manually to locate the break in the circuit.
Remember that it is best to use the trailer cord ground as the reference when you are validating power in the circuit, if you just use a random chassis ground, it could lead you down a rabbit hole .
If you are confident in your checks, I would inspect the wires at the rear corners for any loose connections and if that didn’t bear fruit, it’s time to get into the underbelly and trace the circuits to find the break. As a suggestion, it might be wise to look in the slide out areas to see if something might have gotten tangled up or rubbed thru.