Troubleshooting Right Side Trailer Lights Not Working, Left Side Working Correctly

Question

Question:

have a problem hitch plug. everything on the left side works but nothing on the right. i have checked and tested every fuse and all is good. any ideas

asked by: Dawn

0

Expert Reply:

Most trailer wiring problems are the result of a bad ground. What I would do is start with the connectors. Maker sure the connectors on both the trailer side and vehicle side are free of dirt and corrosion and that they are properly grounded.

Next, I would move on to testing the vehicle side connector using a circuit tester like # PTW2993. Since the right side is not working, you will want to test the pins of the connector for right turn and brake. If looking at the face of the connector, it is the pin in the 3 o'clock position. If you are getting the proper signal at the connector, you know that the problem is on the trailer side.

On the trailer, make sure the main ground is connected to a paint, dirt, and corrosion free bare metal surface on the frame. With the trailer connected , you can test the wiring behind the plug with a circuit tester to verify the signal is getting through. If it is not, then you know there is something wrong with the trailer side connector.

If the signals are getting through, you can move on to checking the wiring back to the lights looking for an broken wires or loose connections. Trailer lights usually ground through their mounting studs unless a ground wire is present. These ground connections should also be free of dirt and corrosion

expert reply by: Michael H

0

Brett P.

6/22/2020

I have led light on my trailer all the lights work accept the drivers tail light why is that

Reply

Chris R.

6/25/2020

Since it's just the left side we can at least be pretty confident that the issue is on the trailer side (and not on the tow vehicle). Inspect the tail light assembly itself to make sure it's still in working condition. You might apply 12V power directly to it to ensure the bulb isn't out. Also make sure it's securely grounded to a clean, bare piece of metal (whether it grounds through a dedicated wire or through its mounting hardware). Let me know what you find and we can keep troubleshooting if needed.

Reply

Sonny

4/11/2021

All running lights have their own ground wire.

Reply

Manuel

8/21/2024

@ChrisR thanks Chris it was the trailer ground,now it's back on the right track thanks again

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See All (4) Replies to Brett P. ∨

Answer 1

Your brake lights and turn signals for each side are on one circuit. The left side turn signal and brake light is generally the yellow wire going into your trailer connector. The first thing to do is check the fuses on your tow vehicle. Next, inspect…

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Answer 2

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part #PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. If the voltage…

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Answer 3

This sounds like a ground problem on the right side. The turn signal not working makes sense because with the brake lights, there is a constant signal coming through which is enough to make the lights illuminate on both sides like they should. But…

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Answer 4

It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side…

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Answer 5

The first thing that I would recommend checking are the ground connections for the trailer side connector and the lights. Poor ground connections are the most common culprit of trailer wiring issues. The lights will have either a ground wire or they…

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Answer 6

Since all of your trailer lights operate properly with the exception of one of the running lights, this tells us that the vehicle wiring harness is probably working properly. I would first carefully check the bad light's ground and power wires to…

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Answer 7

You will first want to check the fuses on your tow vehicle. Some vehicles could have fuses for operating the turn signals and brake lights of a towing package. You will want to check if they are installed and working properly. The next thing is to…

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Answer 8

Thank you for all of the details in your question. It looks like you have a faulty ground or some corrosion in one of your connectors. On a trailer the functions for your turn signals are also tied into the brake lights so if your right turn signal…

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Answer 9

The only trailer wiring options we have for your 2002 Toyota Tundra is 4-ways like the part #118378 which you could convert with a 7-way adapter like the part #37185 which also happens to have a 4-way on the side of it like you wanted.

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Answer 10

First, disconnect the trailer from the tow vehicle so you can check the vehicle side connector. Using a circuit tester like part #PTW2993, test the functions of the connector; specifically check the right turn/brake, to make sure the signal is making…

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Answer 11

The most likely cause for the turn signals not to work when the running lights are on with your trailer is a bad or weak ground. It's very possible that a weak ground connection can be just strong enough to allow sufficient current for some…

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Answer 12

Even though I cannot comment specifically on the grease you used because I am not familiar with it, I can tell you the best grease for trailer bearings is a a grease with a rating of GC-LB, which just means it is made to withstand very high…

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Troubleshooting Right Side Trailer Lights Not Working, Left Side Working Correctly

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