Trailer Wiring

[Jschara]

I could use some help with my trailer wiring. From the plug I ran a white wire on each side back to the tail lights. Using the car plug as ground.
Then I ran a green & brown wire back to the tail lights. I connected White to white on the tail light and brown wire to brown wire on the tail light light and then green to green on the tail light.
On the other side I did the same. Connected white to white brown to brown and yellow to yellow. From there I connected the running lights. White to white and brown to brown. Then ran a brown wire (dotted line) from the right side to the left side.

When I turn on the lights the tail lights work as should. Blinker, tail light and brake lights all work fine. The marker lights don't work.

From my diagram can anyone tell me why the marker lights won't come on.
Thank you, Jim

 

[The Cobbler]

either no ground, no power or bulbs are bad .not sure why you ran the brown across the trailer to marker lights when you are feeding each side already
white is ground in all cases ? led lamps ? ground & hots mixed up?

 

[Jschara]

Thanks Cobbler for the response. Like I said the ground is from the car plug. The bulbs a new led. Actually the whole wiring harness and fixtures are new. I don't understand how the grounds can be mixed up because all white wires are to white wires. I ran the brown wire across the trailer because I saw it in a owners manual. I know now that doesn't make any sense. I did use the type of connectors that crimp the wire together for a splice. I will disassemble and solder the wires.

I will update as I make progress, thanks again,

Jim

 

[JeepYJ]

Why aren’t you also grounding the white (ground wire) at each light directly to the trailer frame?
If you’re tapping into the brown wire on each side there isn’t a need for a jumper. Some trailer plug harnesses only have one brown wire then you need to jump from side to side.
Crimp on connectors (not Scotchloks) are fine, no need to solder the connections. Just make sure they’re sealed with heat shrink tubing.

 

[Firebrick43]

You wired it correctly according to your diagram. The brown wire across is not needed but won’t hurt either.

Can you take off the marker lights and test them to 12v directly to make sure the function and that the polarity is correct? Start simple, new does not mean that they will necessarily is good.

A ground to frame is a good practice but it should still work if the way you have wired it (if your diagram is right and obviously the tail lights are functioning correctly

 

[walta]

If you connected it as shown it should be working.

Are the marker lights new or used?

Try removing one of the markers and testing it with a battery to make sure it works and you understand its connections.

Also connect the white wire to the trailer frame someplace.

Walta

 

[75gmck25]

Simple test -
- find the terminal for the brown wire in the plug on the car - do you have 12 volts with the lights on?
- at the point where the brown wire connects to the marker light socket on the trailer - do you have 12 volts with the lights on?

 

[Jschara]

Why aren’t you also grounding the white (ground wire) at each light directly to the trailer frame?
If you’re tapping into the brown wire on each side there isn’t a need for a jumper. Some trailer plug harnesses only have one brown wire then you need to jump from side to side.
Crimp on connectors (not Scotchloks) are fine, no need to solder the connections. Just make sure they’re sealed with heat shrink tubing.

I ran the ground wire from the plug all the way back on each side of the trailer as to eliminate the need to ground to the frame. I thought that was the best way?

 

[Jschara]

If you connected it as shown it should be working.

Are the marker lights new or used?

Try removing one of the markers and testing it with a battery to make sure it works and you understand its connections.

Also connect the white wire to the trailer frame someplace.

Walta

I will test the marker lights to see if they are good. Thanks for the tip.

 

[Sumboodie]

Need 4 wires.

Ground, turn/brake right, turn/brake left, and taillights/clearance lights.

Edit... maybe you did. The picture is too blurry to fully make out.

 

[JeepYJ]

I ran the ground wire from the plug all the way back on each side of the trailer as to eliminate the need to ground to the frame. I thought that was the best way?

Some people like to run ground wires all back to a central ground point on the trailer which is also where they ground the trailer plug. You should still ground it at the light fixture IMO, other wise you’re making more failure points with lengths of wiring and connections all over the trailer.

 

[Firebrick43]

A dedicated ground is much more reliable than using the trailers chassis itself as a ground path as long as good sealed **** splices are used.

Most older lights used the frame as ground directly via mounting screws for the light itself.

Newer lights, especially LED on high quality class 8 trucks/trailers are almost universally using dedicated grounds. Only time I see hack work using the frame anymore is in truck beds/bodies installed by hack out fitters.

 

[Jschara]

Problem Solved. I re- did the connections with solder. Must have been a loose connection. I wished I had done this from the get go.

Thanks to all who responded. I appreciate your time spent on my problem.
Cheers, Jim

 

[Max]

Problem Solved. I re- did the connections with solder. Must have been a loose connection. I wished I had done this from the get go.

Thanks to all who responded. I appreciate your time spent on my problem.
Cheers, Jim

Good job. If you didn’t this time, next time use heat shrink tubing with adhesive for the joints. It gives better weather protection as well as support for the joint transition from solid solder to the flexible wire.