Trailer Lights Wiring Problem/Question

[Hawg]

It's always the ground! I know, but this time maybe not.I have LED tail lights. The tail lights and the brake light work off the same wire to the plug. The tail light works but the brake light doesn't. I have more redundancy in grounds than you can count almost, so wouldn't you tend think a diode or something in the LED taillight itself? The other tail light and brake work and the grounds to the two tail lights are both connected to a mutual ground, grounded to the frame individually, PLUS another ground running to the front plug. I have to think it's grounded. Light itself?

[john.wells]

Are the lamp assemblies removable and interchangeable? If you haven't already done so, I would start by doing just that, then go from there.

[Blackhawkxp]

Not sure if i am following you completely but i dont believe the brake light and the tail light should use the same wire. You can use the same ground but the signal wire should be different for the brakes. Unless there is some configuration i am not aware of? Can you clarify? If the brake light has power to it then the light is more than likely faulty.

[Sea Hage]

Look at your trailer connector, there are 4 wires, white is ground, brown is tail lite, yellow is turn and green is other turn. The turn and brake work on the same wires, when brakeing the 12 volts is applied via the brake switch, when turning the power is applied via the turn switch. If you have turn signail on and step on brake the flashing stops because it now has a steady power supply.

[john.wells]

Not sure if i am following you completely but i dont believe the brake light and the tail light should use the same wire. You can use the same ground but the signal wire should be different for the brakes. Unless there is some configuration i am not aware of? Can you clarify? If the brake light has power to it then the light is more than likely faulty.

It is possible with CAN (controlled area network) wiring. Digital signals and different frequencies are sent through a single wire to control multiple components (a lot like how DSL internet works through phone lines). http://www.ni.com/white-paper/2732/en/ That said, I doubt the trailer is configured in this manner, it is more specific to the vehicle. I would put money on either a corroded or broken circuit, but those led lights DO fail, although they are really quite reliable.

[Hawg]

My mistake, turn and brake work off the same wire but problem remains the same, 1 brake works, all markers work, and both turns works. It as to be the light.?.?

[B-man715]

Did you test the wires with a voltage meter?

[Hawg]

Not yet, but won't it just say 12 volts? The other lights work, even the emergency flashers.

[B-man715]

Not yet, but won't it just say 12 volts? The other lights work, even the emergency flashers.

It should.

Put your 4 way flashers on, then your tester on the hot wire and the ground wire the light plugs into at the back of the trailer. You should get a flashing 12.x on it, or if you use a test light it will blink in cadence. If that's the case the light assembly is faulty, or has a bad connection right there.

If you aren't getting anything, try grounding the tester on the frame, which will tell you if the ground is bad. Then the search starts to see where the ground is disconnected or corroded.

Hope this helps

Edit: Are you saying the 4 way flasher blinks on the faulty side but not the brake?

[Hawg]

The flasher and the brake is the same isn't it? The brighter intensity. But yes, the flasher work and look to be as they should. I really need to pull the light apart and do some testing.

[B-man715]

The flasher and the brake is the same isn't it? The brighter intensity. But yes, the flasher work and look to be as they should. I really need to pull the light apart and do some testing.

Yes, something is odd. The hazard and brake power come from the same wire and the same ground with the same voltage.

Are the brake lights on both sides inoperable? Or is it just one side?

Both sides= something is wrong from the truck (between the truck plug to the brake pedal switch)

One side= something is wrong on the trailer (from the the plug to the faulty light) But if the hazards work I'm at a loss if everything is wired correctly. Have the brake lights ever worked properly?

[eagle_3464]

If I understand correctly, the brake issue is just one side. If that is the case it comes back to 90% of electrical problems being ground related. The tail light and turn signals work because they require less amperage than a full on brake. Your ground on that side is likely adequate for the lower amperage required for the tail/turn but not adequate for the higher amperage stop. LED requires much lower amperage than incandescent so lots of times people get by with a poor ground. With incandescent you will sometimes see a dimly lit light when you have a poor ground. I would try a positive ground jumper to see if that solves the problem. Good luck.