trailer lights

[ugabulldog]

I am really trying to figure this out, hate trailer lights not working like most people, don't want to rewire entire trailer, but I am close..... It is the trailer as my other trailer works fine hooked to same vehicle.... only 1/2 the lights work, it is not the bulbs... the front running lights work when hooked to truck, but the rest of running lights do not work at all.... but when I troubleshoot and jump trailer pins with alligator clips off of a known good battery, I can't get lights to come on? And I know I am touching the right pins on plug, In fact when I hook up volt meter to leads, it reads 12v but as soon as l I touch leads to plug pins, voltage goes away...... Also, when hooked to truck and front running lights are on, the voltage on wire right before going into front running lights is 20 volts?

 

[LouNY]

does this trailer have electric brakes and a break away switch with its own battery?
Has it been activated and does it go to some of the lights?
That's the only way I could see that you could have 20 volts is 2 batteries in series.

 

[Tomtint]

90% of the time with trailer light problems.. there is a bad ground somewhere.

 

[JLwoodworks]

90% of the time with trailer light problems.. there is a bad ground somewhere.

Yup. When I rewired my trailer I pipe to the entire thing in plastic electrical conduit. I also ran a ground wire instead of using the frame. Everything soldered no crimp connectors. Silicone Dielectric grease is also an important element. In all the bulb sockets and any connectors

 

[PILOON]

Most trailer wiring depends on the frame for the ground return.
One secret is to use a wire loom that includes its own ground wire, forget about using the frame.
Also do not use easy crimp connections, solder each joint and then shrink a waterproof sleeve over that joint.
Corrosion (rust) is your enemy!

 

[WM75Guy]

It is usually the ground on my trailers that cause issues. My smaller Big Tex stop, tail, and marker lights on the rear did not work on the last pre-trip inspection. The front markers and license plate lights worked. Pulled the left taillight out of the rubber housing and found that all the grounds were connected to a bolt through the frame behind it. Tightened the nut and everything worked great. Just lucky I pulled the correct light first.

 

[downsizingnow48]

Probably be time ahead to rewire the trailer. Quite a while ago I bought a 250 ft spool of 16/3 flexible power cord like is used on power tools. Among other things I've used it to rewire two trailers. Not a time consuming job at all. Provides a separate ground wire like Piloon says. Soldering and shrink sleeves also real good advice.

 

[RandyT]

Read someplace that you are not suppose to solder and shrink tube the connections because the solder will move up inside the insulation and the vibration and bouncing causes the wires to break. I have never had it happen, and I have rewired my last two trailers by solder and shrink tubing and running a separate ground to each light.

 

[ugabulldog]

does this trailer have electric brakes and a break away switch with its own battery?
Has it been activated and does it go to some of the lights?
That's the only way I could see that you could have 20 volts is 2 batteries in series.

Yes, it has a battery for breakaway brakes, it has not been activated as far as I know, not activated now anyways...I will check to see if it goes to any lights tomorrow

Read someplace that you are not suppose to solder and shrink tube the connections because the solder will move up inside the insulation and the vibration and bouncing causes the wires to break. I have never had it happen, and I have rewired my last two trailers by solder and shrink tubing and running a separate ground to each light.

A couple of questions on rewiring, where do you ground all the wires to, trailer frame? Also, on lights like these, where the rivet is the ground, where do you attach the ground wire to light?

 

[GLyford]

Does that fixture have a bare metal back where the ground contacts the frame, how does it ground normally? Maybe a ring terminal trapped between the backing and the trailer frame? As I understand it, the most common way of running separate ground wires is not wire OR ground through frame, but wire AND ground through frame, in other words don't take any extra steps to isolate the light grounds from the frame, just provide a better dedicated electrical path in addition so as not to rely on the frame ground.

Here's another troubleshooting thought, regarding battery vs vehicle: Are you actually getting any ground contact through your connector at all? Maybe it only partially works when hooked to the tow vehicle because the ground is happening though the hitch ball (or pintle). Have you tried leaving the wiring hooked up, but unhitching so the hitch is not providing a 2nd ground, then seeing what happens with just the connector ground? The matching battery test would be to add a jumper wire from the battery ground to the frame to bypass the connector.