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Troubleshooting Trailer Light Wiring Problems

Troubleshooting Trailer Light Wiring Problems

For many people, trailer wiring repair is an infuriating encounter. However, the key is to ensure that the root of the problem has been diagnosed early on. It is highly recommended that you use a 12-volt stick-tester to examine the continuity of your wiring and plug which is essentially the first step in electrical repair.

While plug testers are made available for several types of trailer plugs, a stick tester is paramount if the reason for use is on a receptacle. Additionally, a stick tester is capable of testing wiring between connections, and they often come as affordable.

The first thing is to plug the trailer wiring into your tow vehicle while turning on the running lights. Ensure you walk around the trailer so you can examine for yourself if the lights are switched on. In the event that the tow vehicle blows a fuse, the first thing you should remove the tail light lenses of the trailer and check if certain bulbs are blown. Also, you should ensure that the bulb is fit incorrectly. You should always note that the standard for a trailer tail light is the "1157" bulb. You can install this by a means of fitting it into the electric socket while twisting it in order for the contacts to lean on the tail light prongs.

The next thing you should take a look at is behind the taillights and the each trailer marker light to ensure that the hot leads between the light housing are not crushed as a result of improper installation. If this happens, you should pull away from the housing and ensure that the wires are run via the right channel so you could avoid smashing them during re-installation. In the possible event that some wires are exposed, you should replace them with another wire [insulated].

While the lights are still on, use the ignition key to operate turn signals either in the left or right directions. This time, you should walk around again to see each turn signal. If any lights are flashing, then you have bad ground. To solve this, you have to unplug the trailer while connecting the light tester ground to the ground terminal of the tow vehicle. Switch on the running lights alongside the turn signal by putting the stick tester to the terminals. If all functions are still not working properly, ground the tester to the tailpipe and re-test. If the tester is now lighting without the plug ground, then you should ground the tow vehicle. Some vehicles come with 7 pin trailer wiring, and their wires may have to be replaced.

If certain functions of the plug are working correctly, it is very likely that the ground is working just fine and all you have to examine is the wiring as well as the fuse being connected to the plug. Also, test all the functions connected to the 'Converter Box.' If bot turn and brake are coming from the box and are not working out of the box, you should know that the converter box is bad. To solve this, you have to snip the wires while splicing another wire into the wiring joint.

Some vehicles come with factory tow packages, having a unique fuse block designed for towing. In this type of vehicle, if you notice that the signal is not reaching the plug, use the owner's manual in order to find the towing package fuse placement and extract them one after the other. Nonetheless, you should remember that tow packages are mostly located beneath the hood.

Now that the vehicle wiring has been deemed fit to operate, you should plug it again into the trailer and take a look at the lights. If the lights are still flashing on and off with turn signal and tail lights on, it means that the trailer ground is bad. Take a look at the white wire attached to the plug and ensure it is rightly fixed to a frame that is temporarily fixed to the trailer tongue.

You may need to run a ground wire to the trailer light or to the trailer's tilt bed. This way, the lights can make use of the tow vehicle's ground.

About the Author

Hi, I’m Johnny Shelton with NC Trailers, the #1 rated trailer dealer in the Carolinas. With over 300 trailers in stock, we’ve proudly served contractors, adventure seekers, and everyone in between since 1996. Having sold and serviced over 10,000 trailers, we’re grateful for the trust our customers have placed in us. We’re committed to using our experience to help you succeed in all your trailer and towing needs. Let’s thrive together!

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First Last N.
12:41 13 Apr 25
Nctrailers Team are awesome !!! Sam the sales representative was very helpful on the phone and when I should up on site. Shanice with my contract. Tammy explaining each process during the DMV registration and paperwork. Ryan was very patient in the pouring rain preparing and getting me connected to the truck and doing the safety checks 5 times to make sure no issues. Thanks nctrailers of Thomasville for professionalism and attention to detail. I definitely be seeing you guys in a few months for a car trailer .
First Last N.
12:41 13 Apr 25
Nctrailers Team are awesome !!! Sam the sales representative was very helpful on the phone and when I should up on site. Shanice with my contract. Tammy explaining each process during the DMV registration and paperwork. Ryan was very patient in the pouring rain preparing and getting me connected to the truck and doing the safety checks 5 times to make sure no issues. Thanks nctrailers of Thomasville for professionalism and attention to detail. I definitely be seeing you guys in a few months for a car trailer .
Desiree B.
18:02 12 Apr 25
Had the pleasure of buying our first trailer for our new business from them this weekend. And let me say I can’t say enough about this company. From the first call with Donna, till we drove off the lot hooked up, they were absolutely amazing! Their inventory is intensive yes, but the customer service is extraordinary! Our purchase experience start with a transfer to Zach who was welcoming and extremely knowledgeable! Shancie took care of the financing and made everything so easy and simple, and Tammy was fast with our paperwork! Noah and Ryan went above and beyond for the install and hookup of all the accessories we choose! These folks are the best around and hire the most wonderful crew! Highly recommend them for any trailer purchase or service needs!
Desiree B.
18:02 12 Apr 25
Had the pleasure of buying our first trailer for our new business from them this weekend. And let me say I can’t say enough about this company. From the first call with Donna, till we drove off the lot hooked up, they were absolutely amazing! Their inventory is intensive yes, but the customer service is extraordinary! Our purchase experience start with a transfer to Zach who was welcoming and extremely knowledgeable! Shancie took care of the financing and made everything so easy and simple, and Tammy was fast with our paperwork! Noah and Ryan went above and beyond for the install and hookup of all the accessories we choose! These folks are the best around and hire the most wonderful crew! Highly recommend them for any trailer purchase or service needs!
Mitch O.
12:47 12 Apr 25
I would like to take a minute and recognize several people at NC trailers. From the start it was Zach & Sam in sales which went above and beyond the process of helping me pick the correct trailer and helping me complete all necessary paperwork when I was literally 1800 miles away driving down the road.

Shanice in financing made financing the trailer simple and quick, and behind the scenes Tammy in tag/title department was doing her magic so it all came together as one cohesive unit the day of picking the trailer up.

Speaking of picking up the trailer, Ryan & Noah truly went above and beyond expectations working in the pouring rain, while not compromising standards of making sure everything went smoothly and that I was hooked up correctly while taking the time to fully go over every aspect of the trailer and how to hook and unhook the trailer.

Tyler in Service & Parts was very helpful with information regarding the Gooseneck hitch for my next trailer.

Thank you to each Team member of NC trailers. I HIGHLY recommend this company to anyone needing a trailer.

So, if you need any type of trailer, accessory or even a repair, NC trailers should be your First and only stop. They truly make you feel like Family and the trailers are rated top in the Industry and priced very reasonably.

Head on over to NC trailers and get your trailer today. Tell them Mitch with a “M” not a “B” sent you, and you should receive an extra smile or two.
Mitch O.
12:47 12 Apr 25
I would like to take a minute and recognize several people at NC trailers. From the start it was Zach & Sam in sales which went above and beyond the process of helping me pick the correct trailer and helping me complete all necessary paperwork when I was literally 1800 miles away driving down the road.

Shanice in financing made financing the trailer simple and quick, and behind the scenes Tammy in tag/title department was doing her magic so it all came together as one cohesive unit the day of picking the trailer up.

Speaking of picking up the trailer, Ryan & Noah truly went above and beyond expectations working in the pouring rain, while not compromising standards of making sure everything went smoothly and that I was hooked up correctly while taking the time to fully go over every aspect of the trailer and how to hook and unhook the trailer.

Tyler in Service & Parts was very helpful with information regarding the Gooseneck hitch for my next trailer.

Thank you to each Team member of NC trailers. I HIGHLY recommend this company to anyone needing a trailer.

So, if you need any type of trailer, accessory or even a repair, NC trailers should be your First and only stop. They truly make you feel like Family and the trailers are rated top in the Industry and priced very reasonably.

Head on over to NC trailers and get your trailer today. Tell them Mitch with a “M” not a “B” sent you, and you should receive an extra smile or two.
Anthony T.
21:34 10 Apr 25
Awesome place to do business!
Anthony T.
21:34 10 Apr 25
Awesome place to do business!
Shaun O.
04:19 09 Apr 25
I have to say I had great experience with the staff at NCtrailers in Thomasville, NC. The staff up there were amazing. I had the pleasure of being David’s first sale for his new career dealing in this type of equipment. He has had many years in sales and it shows but he decided to venture into a new atmosphere of sales. Working through the contract side of things Shanice was very thorough and was able to give me all the details I needed. She was so inviting and made you feel comfortable through would could be a stressful process.

Tammy was a sweetheart with the tag and title paper work and talked me through all the necessary links and info I would need to setup the last little bit of info.

Ryan and Noah had me all hooked up and ready to go and even took the time to help me find a short in my connection on my truck so I would be comfortable knowing all the lights and everything worked properly on the new trailer.

All in all I had a great experience with the entire staff from parts to sales to service. I will most definitely be recommending them to anyone I know for their trailer needs.

Now wish me luck on my lawn care company venture.
Lawn Legends LLC.
Shaun O.
04:19 09 Apr 25
I have to say I had great experience with the staff at NCtrailers in Thomasville, NC. The staff up there were amazing. I had the pleasure of being David’s first sale for his new career dealing in this type of equipment. He has had many years in sales and it shows but he decided to venture into a new atmosphere of sales. Working through the contract side of things Shanice was very thorough and was able to give me all the details I needed. She was so inviting and made you feel comfortable through would could be a stressful process.

Tammy was a sweetheart with the tag and title paper work and talked me through all the necessary links and info I would need to setup the last little bit of info.

Ryan and Noah had me all hooked up and ready to go and even took the time to help me find a short in my connection on my truck so I would be comfortable knowing all the lights and everything worked properly on the new trailer.

All in all I had a great experience with the entire staff from parts to sales to service. I will most definitely be recommending them to anyone I know for their trailer needs.

Now wish me luck on my lawn care company venture.
Lawn Legends LLC.
Conard B.
14:22 07 Mar 25
The staff was very helpful and motivated I went back and forth with two trailers figuring prices and add ons they were very patient and provide me with two different layouts for two different prices. I finally made my decision. I would highly recommend for your next trailer go too NC trailer sales.
Conard B.
14:22 07 Mar 25
The staff was very helpful and motivated I went back and forth with two trailers figuring prices and add ons they were very patient and provide me with two different layouts for two different prices. I finally made my decision. I would highly recommend for your next trailer go too NC trailer sales.

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