Have a trailer and have no tail lights and/or brake lights. I have both blinkers but they appear dimmer then they should normally be in my opinion. I have power from the truck and past the trailer plug in. Thought it was a ground issue but totally replaced the ground at the receiver end. What else am I missing. Has to be something stupid just curious before I dig deeper into it. Thanks for the help!
Try new bulbs? Does not get more simple than that.
There is a ground at every fixture.
The one connection that is common to the brake lights and running lights is the “ground”. This is the white wire on the connector that is usually bolted down to the trailer frame on the tongue. Make sure the metal is clean and shiny where that wire is connected. Depending on how your trailer is constructed, there may be several different pieces bolted together. There has to be conductivity through all of those joints before you get back to the light assemblies. If there isn’t, you might need to run a dedicated ground wire from the connector all the way back to the light assemblies. Each light assembly is connected to “ground” through the mounting bolts. Once again, clean off the metal where the lights bolt on to make sure they make a good connection there.
Some more detail can be found here:
Good luck!
Rootski
Quote:
Have a trailer and have no tail lights and/or brake lights. I have both blinkers but they appear dimmer then they should normally be in my opinion. I have power from the truck and past the trailer plug in. Thought it was a ground issue but totally replaced the ground at the receiver end. What else am I missing. Has to be something stupid just curious before I dig deeper into it. Thanks for the help!
The issue is indeed the “ground”. Most permanent solution is to run a dedicated “ground wire” from the trailer plug to each light assembly.
If your wires run inside the trailer frame, make sure that the insulation hasn’t been rubbed through and the bare wire is not touching the metal frame. I had the insulation rub off on a tube weld and some lights were dim and brakes were not working as well as running lights. How does one find this? Using a good multimeter on ohms or continuity check(beeps if connection)and touch the ground near the power wires going to the light sockets that are not working. If you get a continuos beep tone or the ohm reading is low, your power wire is touching metal where it should not. Pulling the new wire through the frame may be the hard part. This can happen and not blow any fuses!
So is it possible one left and right are dim and no tail lights and still have a bad ground? I am wondering if I have a wire somewhere that is rubbed through and causing my issue. The lights are LED so I don’t think they would fail but they could.
Also check to make sure your vehicle ground is clean and working properly. It definitely sounds like a grounding or grounded out power issue to me.
Dim blinking turn signals and no running lights is an indication that you have a bad ground. The power to the turn signal element is taking the easier route by feeding back through the tail light element and finding a ground through the power wire to the tail lights.
Ensure that all connections are clean and working well. This means the bulb and socket, the ground wire for the light fixture, all wiring, and the ground wiring at the hitch. Sometimes using a jumper wire with aligator clips between the trailer and the tow vehicle will show that there is a bad ground at the hitch area. Some trailers are wired so they rely on the hitch itself to complete the ground circuit. In a worst case situation, a new wiring and light kit can be installed.
See if a buddy can hook up to it and if problem still happens I fought a ground issue rewired trailer ended up being the vehicles ground 
had this problem–it was a tilt trailer and the hinge pin was rusted up –no ground –fixed the pin and good to go==good kuck
When this issue came up on mine I made certain that the white wire from the plug end attached to the trailer got a solid ground and then I added a ground wire from the trailer frame to one of the attaching bolts on each tail-light unit being sure the ground wire from each unit went to the stud with the jumper connector. I was assuming that the tail light brackets were sufficient ground and they were not. The jumper ground solved the problem.
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