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Troubleshooting Trailer Light Wiring Problems

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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 not 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] from our trailer parts counter.

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 both 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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Mike J. profile picture
Mike J.
1 week ago
Great and easy experience from start to finish.
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Wesly H.
2 weeks ago
My experience was great
Ryan is awesome
Shanice was great Tammy was so helpful
Noah did a awesome great
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Butch F.
3 weeks ago
We had a really great experience buying a trailer from this dealer. David was so knowledgeable & answered all my questions. Shancie and Tammy were very pleasant & helpful in handling all the paperwork. We will certainly recommend to friends to come here for their needs. Butch & Donna Franklin
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David N.
3 weeks ago
I called and needed something to haul a car on short notice/same day. Carter in Winston Salem found what I needed at the Thomasville location, had the ball rolling on the paperwork and everything within minutes.
I arrived at the Thomasville location and was immediately greeted by and taken care of by Sam. She treated me as if was her own customer and was amazing. Everyone there was super helpful from Shancie in finance, to Tammy who handled my tags to Christian who hooked me up and answered all the questions I had and even the parts/service guys getting my hitch etc.

This was by FAR the best sales experience I’ve ever had hands down. If you need a trailer call Sam in Thomasville or Carter in Winston!
Matt W profile picture
Matt W
3 weeks ago
Can't express how incredible it was doing business with NC Trailers. Had a trailer delivered to the Thomasville location from Winston Salem in no time and everyone there was incredibly helpful and nice. Highly recommend NC Trailers.
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Sandra S.
3 weeks ago
Fantastic place to book your transfer, the staff is excellent and helpful in getting you a great deal. 100% recommended!
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Derek D.
4 weeks ago
Was looking online for a max d buggy hauler for my jeep the website sent me here. Sam Marsh took care of me was a pleasant experience all the way around everyone was courteous helpful. New trailer was a great experience. Already in talks for the next one
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Ron C.
4 weeks ago
That is the best service I have ever had buying something. Sam,Christian,Shoncu,Annite these are the nicest people to work with
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Brett J.
4 weeks ago
Fantastic buying experience from start to finish. The entire Thomasville team at NC Trailers made the process completely hassle‑free. Huge thanks to Ryan, Shancie, Annette, Christian, Noah, and Tony for their outstanding service. Their inventory is extensive and ready to roll. I was able to drive off the lot the same day. Highly recommend them to anyone looking for a fast, smooth, and quality transaction. Outstanding business and outstanding people.
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Donald E.
4 weeks ago
Yeah I would like to thank Justin and Tyler for the excellent job they did on my bike trailer yes it was a little expensive but it was worth the time and the effort to take it to them to have it repaired very satisfied. Donald Emery Hillsborough North Carolina
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BelAire A.
4 weeks ago
Sam was great to work with
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Steve Y
4 weeks ago
Purchased a 6x12 Nolan trailer today, Dave in Sales assisted and did a great job showing me the trailer and explaining the features and working thru the paperwork; Shancie assisted with processing the registration & tag paperwork and getting all the appropriate paperwork for that filled out; and Christian assisted in getting the trailer hooked up and explaining important items regarding safety, maintenance, etc. Overall very pleased with the transaction and the service received and highly recommend NC Trailers to perspective buyers.

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