Right Turn Signal and Brake Light Not Working on Trailer

Right Turn Signal and Brake Light Not Working on Trailer

The turn and brake signals are crucial in a trailer just as they are in a vehicle and help keep other drivers safe. Therefore, they must function at all times while the trailer is in use. And when the right turn signal and brake light fail, the cause must be determined and fixed soon.

So, why would the right turn signal and brake light not work on a trailer? Some of the reasons these right-side lights may not work include corroded connectors and wiring issues. A faulty harness and grounding issues may also be a possible cause. Get the connectors checked to determine and fix the problem.

This article addresses the issue of the right turn signal and brake light malfunctioning and explains some potential causes. Keep reading.

Reasons Why Right Turn Signal and Brake Light Not Working on Trailer

Reasons Why Right Turn Signal and Brake Light Not Working on Trailer

Following are some reasons the right turn signals and brake light may not be working on a trailer.

1. Corroded Connector Pins

One of the possible reasons the right turn signal and brake light may not work is due to metal corrosion. The two lights share the same pin in the connector, and the two lights won’t work if it’s corroded.

Pins get corroded due to exposure to moisture for a long time, especially on the car side, which is the male port. If the connector is not well secured when not in use, moisture can get in, corroding it.


Disconnect the trailer connector and observe the pins keenly. The right turn signal and brake light pin are usually on the right side of the standard/traditional seven-pin connector.


If the pins are corroded, the solution is to clean them. Buy an electronic cleaner of your choice and follow the steps below.

  • Step 1. Turn off the vehicle.
  • Step 2. Disconnect the trailer electrical connector.
  • Step 3. Spray the rust remover on the pins from both sides of the connector. The other pins may also be corroded, just not as much, so it’s important to spray all of them.
  • Step 4. Allow them time to dry.
  • Step 5. Reconnect and test.

You are likely to spend around $15 for a corroded connector if you want to replace it.

2. Short Circuit on The Right Side

Another possible reason the right turn signal and brake light may fail is due to a short circuit. A short circuit can occur due to electricity overload or contact with a lot of water. Usually, shorts are possible on both sides of the connector, the car side or the trailer side.


To diagnose the connector, test it with a circuit tester. Get a circuit tester and follow the steps below.

  • Step 1. Set the multimeter to 12 volts.
  • Step 2. Connect the positive probe of the tester to the pin on the right side of the seven-pin connector.
  • Step 3. Connect the ground to any known ground source, including a bolt or brackets.
  • Step 4. Depress the brake pedal or turn on the right turn signal.
  • Step 5. If there’s no current detected, it may be weak or non-existent.
  • Step 6. Test the trailer side of the connector to see if there’s power on the vehicle’s side.
Trailer Short Circuit on The Right Side


There is probably a blown fuse if the problem is on the vehicle’s side. Follow the steps below;

  • Step 1. Access the fuse box.
  • Step 2. Check the diagram on the fuse box cover or user manual to learn which fuse is for the trailer’s right turn signal and brake light fuses.
  • Step 3. Observe each fuse if it’s blown.
  • Step 4. If fuses are blown, replace them with new ones.
  • Step 5. Test the right turn signal and brake light.
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Diagnosing and fixing this problem will cost between $100 and $220 if a mechanic does it for you.

3. Wiring Issue

If a diagnosis with a circuit tester shows there’s no current on the trailer side, there may be wiring issues. The wires in the trailers are routed separately from others, and those to the right turn signal and light may be broken or frayed.


Inspect the wire from the connector on the trailer and trace it to the taillight assembly. Check for broken or frayed wires that may be exposed, either touching the trailer and causing a short or interfering with the electric current.

Trailer Wiring Issue


The solution to damaged or frayed wires is to replace them with new ones. Get a compatible wire and follow the steps below.

  • Step 1. Prepare the wire length to match that of the section you want to replace.
  • Step 2. Cut the wires and label them so as not to confuse them.
  • Step 3. Attach the new wires using butt connectors to ensure where you cut the old ones.
  • Step 4. Fix frayed wires by applying electrical tape or shrink tubes.
  • Step 5. Test the right turn signal and brake light.

Fixing trailer wiring will cost somewhere between $75 and $150. 

4. Faulty Harness

Some people use after-market wiring to power the trailer from the tow vehicle. In this case, the harness may be loose or damaged, causing issues powering the right turn signal and brake light.


Check the wiring harness to the trailer to identify any loose connections or broken wires. Most people with after-market wiring use the 4- or 5-pin trailer wiring since they’re easier to use. The right turn signal and brake light usually use the green wire.


Provide the following solution to fix the faulty harness problems if this is the cause behind the two lights not working.

  • Fit the Connections: If there are loose connections on the connecting points of the harness, reconnect them correctly.
  • Fix Frayed Wires: Use hot glue or shrink tubes to fix any frayed wires that might be interfering with the electrical signal.
  • Replace Damaged Wires: Replace damaged wires with new ones. In most cases, this will involve cutting and joining with new wires.
  • Replace the Harness: Replace any damaged harness with a new one.

In most places, fixing a faulty harness problem will cost you somewhere between $45 and $300.

5. Grounding Connection Issues

A loose ground connection is another possible cause behind the right turn signal and brake light not working. Without it, the electrical circuit becomes incomplete, and a reason the lights may not be working.

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Some diagnosis checks to perform include;

  1. Check whether the ground wires are connected securely to the trailer’s frame.
  2. Check whether the ground wire is frayed or broken.
  3. Check the ground on the vehicle’s side and ensure it’s well connected.
Trailer Grounding Connection Issues


The solutions to ground problems causing the right turn and brake light not to work include;

  • Reinstall the ground wire to a paint and rust-free surface on the trailer’s frame.
  • Fix frayed ground wire or replace it if it is badly damaged. 

Fixing ground connection issues will usually cost you below $100.

If you’re facing issues with the right turn signal and brake light on your trailer, our article on brake lights not working but third light is concerns may offer insights that could be applicable to your situation. Additionally, if you’re a Ford Ranger owner dealing with a non-functional third brake light, our guide on Ford Ranger third brake light not working could provide solutions to your issue. We understand the importance of maintaining safety and functionality, and our comprehensive resources are aimed at helping you troubleshoot and address any challenges you may come across.


Following are some related questions to aid you in diagnosing and fixing the issues. 

Q1. Can Burned Bulbs be a Reason the Trailer’s Right Turn Signal and Brake Light Aren’t Working?

Yes. Burned bulbs can be a reason the right turn signal and brake light may not work on a trailer. The bulbs can burn during a short circuit when broken wires touch the vehicle’s frame. Test new lights to check whether that will fix the problem.

Q2. How Long Does It Take to Diagnose the Trailer’s Right Turn Signal and Brake Light Not Working Problem?

Most mechanics can diagnose this problem within an hour and fix it. However, the time will vary with the cause of the problem. For more complicated solutions, like replacing the wiring harness or rewiring the trailer, will take more than an hour.

Q3. Can I Tow a Trailer with the Right Turn Signal and Brake Light problem?

It is not a good idea to drive a trailer with failing lights as it can confuse drivers driving behind you. They may not be able to know when you slow down and apparently won’t know when you want to turn right. For your safety and others on the road, get these lights fixed.

Bottom Line

The right turn signal and brake light are fitted under one wire, a reason they fail together. Some of the causes the two lights may fail include short circuits and wiring issues. Also, corroded connectors, especially the pin to the right side, can cause this issue.

While you can hire a professional to diagnose and fix the problem, you can do it following the steps in the article. However, hire a mechanic to avoid further problems or if you can’t figure out the issue.

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