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## RiparianRanger

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## hupcej4x4x454

Sounds like you have 2 broken wires (yellow and green), bad connections, plug or blown bulbs.
See wiring diagrams below:


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## sherman51

I would venture to guess 2 blown bulbs unless you have led lights on your trailer. could be corroded plug or broken wires going to the lights though. but I would start by checking the bulbs and use a 12v tester to check for power in the light bulb socket.
sherman


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## RiparianRanger

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## tommyboy

Had the same problem mine was a bad ground.


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## SportTroller

If bulbs are good, bad ground!


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## ezbite

mine were really dim, went to auto zone and got a can of electronis spray cleaner. looks like a new system now and check the bulbs.


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## All Thumbs

i was having the same trouble but when i hooked the trailer up to another truck everything worked. it was my connector on the truck. $15 later and a simple swap out and everything is dandy. this don't help you but it is always good to check it on another vehicle like you did.

all thumbs


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## sherman51

have you cleaned the plug on the trailer?? I've had problems in the past where the plug corroded and wasn't making contact. take a little cheap 12v tester and take the sharp point and stick it in the wires going to your brake lights and see if your getting power past the plug.

it would be rare for the wires on both sides to go bad at the same time. but I just had the left tail light and left brake/turn light to stop working. it turned out both wires went bad. I was getting power up front behing the plug but nothing in the back. replaced the wires and fixed my problem. but I'm guessing its the trailer plug.

please let us know when you get it fixed and what fixed it.
sherman


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## Hvymetaleyes

sherman51 said:


> have you cleaned the plug on the trailer?? I've had problems in the past where the plug corroded and wasn't making contact. take a little cheap 12v tester and take the sharp point and stick it in the wires going to your brake lights and see if your getting power past the plug.
> 
> it would be rare for the wires on both sides to go bad at the same time. but I just had the left tail light and left brake/turn light to stop working. it turned out both wires went bad. I was getting power up front behing the plug but nothing in the back. replaced the wires and fixed my problem. but I'm guessing its the trailer plug.
> 
> please let us know when you get it fixed and what fixed it.
> sherman


Dont forget to check your fuses some vehicles have towing fuses under hood


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## sherman51

Hvymetaleyes said:


> Dont forget to check your fuses some vehicles have towing fuses under hood


that's the 1st thing I thought. but the op said he hooked the lights up to another truck and got the same results.

I had a friend come by my campsite up at Geneva last yr and either his brake lights or his running lights wasn't working. I don't remember for sure which lights wasn't working. but I told him that on the newer trucks they had a separate fuse under the hood for the trailer lights. he checked the fuses and found the one that had blown. he replaced the fuse and fixed his lights.
sherman


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## fastwater

Like Sherman referred to, since you have eliminated your vehicle from the equation, and having issues with both back lights, I believe the 1st place I would check would be the actual plug itself like Sherman stated.
The 2nd(and most prone place) is where the trailer plug wires end and connect to the factory trailer wires. 
Other than a ground issue( which you apparently don't have since your running lights are working) this spot is where I find the majority of issues at. Mostly due to the way the wires are joined together. Very often the wires are joined together by either just twisting wires together... or with cheap, hard plastic coated butt connectors that when crimped, usually puts a hole in the hard plastic then taped up. Either way is a sure bet corrosion will eventually set into the connection. 
While there may not be a 100% sure bet 'lifetime' way of eleminating corrosion in an electrical connection, there are ways to drastically cut the chances of issues down. 
IMO (which is worth exactly what you paid for it), the absolute best method of joining two wires for a more trouble free, permanent connection is by :

1st... cutting a piece of heat shrink tubing about 4"long and placing it over the end of the wire and let it slide down out of the way.

2nd...stripping the insulation off one end of the wire to be joined and making a loop on the end by folding the end of the wires back and twisting them tightly around themselves to create the loop in that wire.

3rd... Take the wire you are going to join, strip it back and run it through the loop of the 1st wire. Then fold it over and twist it onto itself. You now have the two wires joined together by the loops.

4th... solder this connection well.

5th...dab on a light coat of dielectric grease on connection and all bare wires.

6th...pull heat shrink up over connection and bare wires and heat it to wire.

7th...(optional, but I like to do it cause it's another protective coating to keep moisture out) wrap complete connection in electrical tape.

This is the process I've had the best luck with as far as longevity in electrical connections.

The 2nd best way I've found is using the good butt connectors that have the heat shrink built onto them. After crimping them, tape the connection well.


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## ReadHeaded Hunter

The brake / turn signals are the "high filament" on the bulb & require a better ground than the running lights. First step is always to establish a good ground, 100% sure on the ground. I use a long piece of wire with little alligator clips on each end & ground to the frame of the truck & a bare metal spot on the trailer tongue. After that, check bulbs for good high filament & a clean connection. Then start from the plug & work your way to the lights, testing behind any connection or splice. Can be maddening if the ground isn't confirmed before starting ....... learned that the hard way many years ago !!


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## sherman51

I just had a problem with my left light on my trailer. nothing on the left side worked. I checked the ground 1st and had good ground. I peeled the insulation off both wires at the light and checked for power. and didn't have power on either wire. went to the front of the trailer where the wires split to go down the sides. I checked both wires and had power. the wires was a straight run to the back of the trailer. I checked for kinks and fraying and the wires were good but didn't have power to the back of the trailer. I spliced in new wires up front and run them back to the light. now both lights works as they should.

one thing I would do is remove the bulb and use a 12v tester and run a ground from the truck and use the tester to see if you have power to the light socket. if you do then you have a ground problem. if not then I would start at the plug and check to make sure you have power behind the plug. then I would start working my way back to the light checking for power until I found none or until I reached the light. if you have power to the wires and ground to the light and the light still doesn't work its probably just a bad light.

I would still check the fuses under the hood if all else has failed. or just check the truck plug to make sure you have power going to the plug. the other truck you used to test the lights could have blown the same fuse. I know not likely but were trying everything. right??
sherman


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## fastwater

Another good post sherman.

Here's a word of caution...when using a 12v electrical test light, the style that pierces a hole in the insulation to check for power, just remember, wherever you pierce that insulation, you're surely asking for future issues down the road with corrosion on the wiring inside the insulation at the point you probed the insulation. Many times theses areas are very easy to miss when inspecting the wiring cause all the corrosion is inside the wiring insulation on the wiring and the insulation looks fine from the outside.
If possible, when using this type of tester to check for power it's always best to check at connection points where the wires are already bare. If you absolutely have to pierce the insulation, at least use some wiring, liquid insulation/liquid tape over the hole you pierced in the wiring. 

When possible, when checking for a 'broken wire' from one connection to another (IE the length of wires running through the frame of the trailer) use a continuity tester. 
Another use for a continuity tester(especially in a case in which wires run through a frame and can't easily be seen) is testing whether the insulation on a normally hot wire has been rubbed through and the normally 'hot' now bare wire is touching or grounded out on the inside of the frame rail causing lt. not to work. If you hook one probe of your continuity tester to the normally hot wire at the plug in connection and touch the other probe of the continuity tester to the trailer frame and it lights the tester, you know somewhere that in that wire there's a bare spot touching the frame somewhere.


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## sherman51

fastwater said:


> Another good post sherman.
> 
> Here's a word of caution...when using a 12v electrical test light, the style that pierces a hole in the insulation to check for power, just remember, wherever you pierce that insulation, you're surely asking for future issues down the road with corrosion on the wiring inside the insulation at the point you probed the insulation. Many times theses areas are very easy to miss when inspecting the wiring cause all the corrosion is inside the wiring insulation on the wiring and the insulation looks fine from the outside.
> If possible, when using this type of tester to check for power it's always best to check at connection points where the wires are already bare. If you absolutely have to pierce the insulation, at least use some wiring, liquid insulation/liquid tape over the hole you pierced in the wiring.
> 
> When possible, when checking for a 'broken wire' from one connection to another (IE the length of wires running through the frame of the trailer) use a continuity tester.
> Another use for a continuity tester(especially in a case in which wires run through a frame and can't easily be seen) is testing whether the insulation on a normally hot wire has been rubbed through and the normally 'hot' now bare wire is touching or grounded out on the inside of the frame rail causing lt. not to work. If you hook one probe of your continuity tester to the normally hot wire at the plug in connection and touch the other probe of the continuity tester to the trailer frame and it lights the tester, you know somewhere that in that wire there's a bare spot touching the frame somewhere.


some good advice here for sure.

I usually peel the insulation back to test the wire then seal with liquid tape. if I do use the probe to test for power through the insulation I seal that spot with the liquid tape. it makes a much better seal than electrical tape.
sherman


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## Crappietrace

Had a similar issue with my truck to bot trailer ... Used a DVM to check the wiring... Turned out the connector on the truck was very corroded for myself as a. electrician It turned out to be a 5 min job


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