Trailer Light Question

[CFFF 1.5]

I am having some issues with the lights on my trailer. I believe the issue is a bad ground wire but I don't know why it isn't grounded correctly. Here is the issue. When I have the lights on my tow vehicle on the brake lights go off when I hit the brakes, but the running lights work fine. Also when I am stopped and turn my turn signals on when I have my lights on the turn signal works but the brake lights still aren't on. I believe I have a ground issue because the lights work fine besides the brake lights when my headlights are on. Here is my setup. The ground wire that comes off my tow vehicle is bolted to the front of the trailer and my trailer lights have a ground wire bolted to the back of the trailer basically using the trailer as the ground. Is there anyway to test the ground wires on my trailer to ensure they have a good ground. The wiring and lights on the trailer are less than 4 years old. The lights are mounted on PVC guide rails and are never submerged under water.

[00 mod]

Either a bad ground, or your plug is wired wrong. Is this a new problem, or has it always been this way? Does it act the same way with a different trailer/

Jeff

[CFFF 1.5]

It has worked in the past so I know that the wiring is correct. I understand that I most likely have a bad ground. How do I check for a good ground. I have gone over the wiring with the exception of the wiring that is fed through the pvc guide rails and everything looks good. I would like to be able to check for ground so I know where I need to start replacing wire/s.

[J Francho]

It sounds more like a short. If there is juice running through the ground wire, you got a short somewhere.

A new harness is less than $10, and wiring it is a snap. it took me a couple hours to do mine, and I lost a fish line in the process, and had to get a wire snake. Use the old lines to pull the new ones through. Solder and shrink wrap your connections and you'll be good for years.

[00 mod]

It sounds more like a short. If there is juice running through the ground wire, you got a short somewhere.

A new harness is less than $10, and wiring it is a snap. it took me a couple hours to do mine, and I lost a fish line in the process, and had to get a wire snake. Use the old lines to pull the new ones through. Solder and shrink wrap your connections and you'll be good for years.

This! Chasing wiring problems will drive you absolutley crazy and it sounds like it would be a good time to replace them anyhow!

Jeff

[CFFF 1.5]

I have a c channel trailer so all of my wiring is basically exposed and available for inspection. I rewired the whole trailer when I bought the boat in 2009. Rewiring will only take me about an hour, but I still believe the issue is a bad ground. Can I check my ground by attaching my ground wire from the lights to the negative side of a 12 volt battery?

I don't believe I have a short unless it is on the vehicle side because the issue happens with both trailer lights. I believe because the issue happens with both lights that my ground issue may be with where the ground attaches to the front of the trailer.

[00 mod]

Check all grounds...there also might be a ground wire that runs off each of your lights! If in doubt, drill a hole through trailer at each spot, then use wire brush to remove all paint/rust(both sides), and then run a nut/bolt through the hole attaching new ground and there should be no ground problems and that is taken out of the equation!

Jeff

[scrutch]

The first thing I would do is disconnect the ground connection where it is bolted to the trailer. Thoroughly check the squeezed on eye connector to make sure the wire doesn't have any broken strands. If theres any concern , cut it off and squeeze on a new one. If its good then wire brush the connector and the spot where it makes contact with the trailer, apply some dielectric grease like Penetrox, and bolt it back together.

If the problem doesn't go away, you might have an OPEN in your ground wire. The way to check this is to test for continuity between the ground pin on your trailer plug and a BARE SPOT on the trailer. Very important to find a good spot where there's no paint or rust to insulate your test. If you have continuity, then you have a good ground. If there's no continuity, then I'd replace the entire ground wire on the trailer.

If you kicked up a rock and hit the wire enough to break it or the wire has rubbed a bare spot in it from vibration, it could produce the effect your having.

Let us know what you find.

[FD.]

It could be a problem on your tow vehicle. I would hook it up to another vehicle if possible. If that checks out then it sounds a short or a ground wire that has most of the strands either broken or a loose connection.

[urp]

Disconnect the ground at the vehicle. Connect a long separate wire to ground at the vehicle and then connect that wire directly to ground at one of the trailer lights. See what that gets you. If the light works properly replace the ground complete.

[TomB]

My 2 cents:

Get yourself a test light from an auto parts store (10 bucks). Unplug the trailer lights and test the feeds coming out of the vehicle.

The brown from the vehicle is ground so clip the spring clip on the test light to the ground from the vehicle.

Test each of the other 3 connectors individually with the pointy probe. One is for brakes, one for left blinker, one for right blinker.

If all work using the vehicle ground then you have a decent vehicle ground. If not trace back the vehicle ground and repair.

Then to eliminate or fix a bad trailer ground, buy 12 foot or so of brown lamp cord from a hardware store or big box. Run the lamp cord from the front ground connection to the rear ground connection. For the test you don't have to be fancy. Reconnect the vehicle to trailer and test the trailer lamps. If they work now then nicely route and connect the new ground wire using soldered terminals if possible. Use both wires of the lamp cord and secure with black strap ties. (never use clear because UV light weakens it)

I suggest lamp cord because it is cheap, readily available, and the multi strands is an excellent conductor. (electrons travel on the outer skin of wire so more strands is a better conductor than a single wire)

Hope that helps!

[Tpayneful]

FYI. If you have a swing away tongue and the ground wire to the vehicle is on the tongue you will eventually have ground problems. The hinge is the only thing connecting the the tongue to the trailer and eventually they rust which electrically disconnects the tongue from the trailer. I had to add a ground from the tongue to the trailer to eliminate the problem. Make sure you have a volt - ohm- amp meter to troubleshoot electrical problems. You can buy a cheap digital one at walmart or harbor freight. Turn the dial on the meter to ohms / continuity and the meter will beep when you have a short between the black lead and the red lead. Starting at the plug, measure from the ground pin to clean metal on the trailer and it will beep. The beep means that you have a good ground connection. Go to the first light and do the same thing on the mounting bolt (which is ground for the light). Do the same thing for all of the lights. Most likely you need to unbolt the light, wire brush the mounting hole to remove rust and reassemble. One thing that would help is to buy a tube of dielectric grease and apply it to the hole and mounting bolt before you remount the light. This would ensure that the light would maintain a good ground for a long time. I would also remove each light bulb in each housing and coat the metal connection points with dielectric grease as well. This will ensure that the light bulb connections will not corrode.

I bought a $10 trailer light set from walmart, used the grease when I installed the lights on my boat trailer and had 5 trouble free years of use out of them.

Good luck