Trailer Wiring

Hey All,

See if I can get some pointers on an issue I have. I connected the boat to the truck last night so I could fish this morning and none of my lights works. I used wire brushes to clean the ball of my truck off and cleaned the inside of the coupler with it. I got a new bold where the ground connects to the trailer and cleaned that area of the trailer off as well. Still nothing. I ran the ground directly to the frame of my truck and still no lights. If I connect a tester to my truck the lighting on there all works. Just the trailer. I have a feeling it’s a grounding issue since none of the lights work but at this point I’m not sure since I get nothing. Do I rewire it all?

Spray some WD-40 on the trailer connector plug to penetrate any corrosion or crud off of the pins. If you have an ohm meter, test the resistance of the ground from the trailer to the truck. Most often it seems to be a dirty plug.

You’re correct in thinking that the problem is with “ground”. That’s the only thing that is common to all of the lights. All three circuits in your trailer return through the trailer frame. That’s why you bolt that ground (white) wire to the frame. On the other end, the bolts that hold the light assemblies in place also make a connection to “ground”. Somewhere in between is where your problem is. Your trailer may actually be made up of several different sections that are bolted together especially near the tongue. You might have to tear those joints apart and clean them up to get a good connection. If it was me, I’d borrow a “fish tape” and pull a ground wire from the front of the trailer right to the back of the light assembly and be done with it.

Good luck!

Rootski

Try removing and reinstalling the hitch or take it around the block and see if it frees something up

With your multi meter, test back at the tail lights to see if there is current. if there is current reaching the lights then that verifies its the ground.

My leading suspect is that you broke the ground inside the plug o. The trailer side.

Grouse

Check a bulb if you haven’t already. Had the same trouble and found all the bulbs blew at once. With a bad ground you will generally still have lights but they will be dim and all flash with a blinker on. Also have had mice chew through entire harnesses! Check to see it there is power in one of the bulb sockets.

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Try removing and reinstalling the hitch or take it around the block and see if it frees something up

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Took it around the block and jumped on it like a freak and nothing.

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Spray some WD-40 on the trailer connector plug to penetrate any corrosion or crud off of the pins. If you have an ohm meter, test the resistance of the ground from the trailer to the truck. Most often it seems to be a dirty plug.

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WD40 I got and will try. How do you use an OHM meter to test the wiring. This is something I never have done.

Not sure about the lights being burnt out since most are LED except the front two lights.

The other question I have is that I put a new wiring bracket on my truck last year. Looking at it today the frame it bolts to is a rusty. Would it be worth while to take that off and clean it all up and put it back on.

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Not sure about the lights being burnt out since most are LED except the front two lights.

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Realized that was a posibility after I posted.

With a test light you should still be able to test to see if there is power at wires leading to the lights.

An OHM meter will show a high resistance if there is a break in the circuit(wire). You can place one prong at the plug and one prong on the farthest light you can reach on the same colored wire. Since no lights are working the nearest will work too. If the gauge shows no resistance the wires are fine. If it shows the opposite obviously there is a wire broken.

To test the ground as Randy mentioned you should be able to place a lead on each ground wire near where they are bolted to the vehicle and the trailer.

I would still test with a test light at the lights themselves first! If you have power there you created the ground to complete the circuit and grounding will be your issue at that point.

Got a meter on it and had no power anywhere after the tongue of the trailer. I had bought a new LED light kit since one of my lights had broken red plastic around it. I put that on and ran the wires back straight from the truck without going through the trailer yet. I get 8 volts back there but no light at all. I took the mounting harness off the truck and sanded it down to bear metal. Did the same where the lights go on. Same thing.

Any clue on this? Has me baffled. I’ve never had issues before.

Something that i have HEARD and BELIEVE to be true, but odn’t KNOW for a FACT is that you can not MIX LED with TUNGSTEN lites any place.

This might be your issue.

I’d replace the rear lites with LED fixtures (it seems to be the future) and run a grounding wire all the way back to each fixture. Then rust and poor conductivity will not be an issue.

But, if you have ANY other lites on the trailer, I believe you have to remove them.

Just curious Stu,why do you think it would make a difference if you mixed LEDs with a regular light?
A friend of mine has LED taillights and normal side markers and it works just fine.
Power is power.

i agree, but it’s not what i’ve heard. maybe there is an electrical engineer who can asplane id 2 us…

Will not matter mixing. We do it on autos everyday.

Pull it around the block a few times then recheck things. “Sometimes” this gets the ground ” trailer to truck” to work.

Stupid ? but did you ground the new harness while testing? 8 volts seems low. Check all fuses on the truck for trouble shooting sake. Have you tried hooking your trailer to another vehicle to see if it works then? Or tried another trailer on your truck? Do you have 12+ volts at the truck plug? If not it may be the truck harness. Is there any kind of box in your truck wiring harness? Sometimes those go bad on the aftermarket plug into the lights type harnesses! This is a stumper for sure.

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Stupid ? but did you ground the new harness while testing? 8 volts seems low. Check all fuses on the truck for trouble shooting sake. Have you tried hooking your trailer to another vehicle to see if it works then? Or tried another trailer on your truck? Do you have 12+ volts at the truck plug? If not it may be the truck harness. Is there any kind of box in your truck wiring harness? Sometimes those go bad on the aftermarket plug into the lights type harnesses! This is a stumper for sure.

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Truck box has full power. It doesn’t matter if you mix LED and regular lights, they’ve been running that way for three or four years.

Here’s what I did. I ran a ground all the back and the lights lit up. So what I did is run the new harness all the way down with a ground wire as well. Then looped back up to the other lights with a running wire and a ground. With all the lights grounded with a ground wire everything is lit up and working great.

It took me a while because I soldered each connection, then spreed liquid electrical tape over them and then used a heat shrink tube. They are rock solid and waterproof. Should last me for a while now. I hope to not have to do it again.

Thanks for all the tips and help guys, much appreciated.

Awesome

I have no idea why trailer manufacturer’s ground their lights through the frame. Stupid if you ask me. It saves what… 2 bucks? And might not cause an issue under warranty but its guaranteed you’ll have a problem at some point. If death and taxes are the only 2 guaranteed things in life, a trailer light issue has to be #3. And its sooo easy to prevent.

Here’s my solutions to all your trailer light problems. 1- Pull ground wires down each side of the trailer and connect lights to them. 2 – solder ALL connections and heat shrink them. 3 – LED lights.

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I have no idea why trailer manufacturer’s ground their lights through the frame. Stupid if you ask me. It saves what… 2 bucks? And might not cause an issue under warranty but its guaranteed you’ll have a problem at some point. If death and taxes are the only 2 guaranteed things in life, a trailer light issue has to be #3. And its sooo easy to prevent.

Here’s my solutions to all your trailer light problems. 1- Pull ground wires down each side of the trailer and connect lights to them. 2 – solder ALL connections and heat shrink them. 3 – LED lights.

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I agree Chris. I shouldn’t have to deal with them again for a very long time.