7 Pin Trailer Running Lights Not Working: 5 Fixes

7 Pin Trailer Running Lights Not Working
7 Pin Trailer Running Lights Not Working

Technology is never perfect so there can be times when your 7 pin trailer lights are not working the way they should. Figuring out what the problem is can be a frustrating process when you aren’t sure all that can be wrong.

Let’s take a look at the possible reasons why 7 pin trailer running lights stop working

7 Pin Trailer Running Lights Not Working

When trying to get the running lights on your trailer to work, you might notice that they are blinking or not turning on at all. They can flicker when a part of the circuit isn’t working properly along with them not lighting up at all.

1. Trailer Plug Corrosion

The most common problem for your 7 pin trailer running lights not working has to do with trailer plug corrosion. This means that your trailer plugs should be the first thing that you look at.

Corrosion will block the electric circuit from properly going through and letting corrosion sit can be dangerous after a while.

Corrosion on your trailer plugs will look like white or green debris on the plug or rust. Sometimes, the corrosion will look bluish. If there is a light amount of corrosion, you should just be able to clean it off and have your lights working again.

To clean off corrosion, you can either sand it away with sandpaper (though you will have to clean the dust off) or you can use an electrical contact cleaning spray and let that dissolve the corrosion.

After you successfully clean the corrosion off, try to use the trailer running lights again.

However, if you inspect your trailer plug and find that the corrosion has built up a lot to where you can barely see the plug, it will save you time and energy to replace the plug.

At that point, a new plug will be needed as the corrosion has done too much damage at that point. For any corrosion still left around the base, let plenty of electrical contact cleaner sit and dissolve the corrosion.

2. A Wire or Screw Isn’t Properly Connected

Over time, wires and screws can come out of place which will interrupt the electrical current and stop your running lights from working. This is a simple problem that has a simple solution.

First, you should check the connection of the wires. Take the cover off of the plug by unscrewing it. Look at the colored wires inside and check to make sure that they are properly connected.

Disclaimer: Never touch wires that have electrical currents going through them, especially without the proper protection. Make sure that the power going to your 7 pin trailer running lights are off and that there is no more electricity running through the wire before getting too close.

There might be screws securing the wires inside of the plug, make sure that they aren’t sticking out of place and are properly tightened.

If you take a look at the screws and wires and find that there is dirt or other debris caked up around either of them, then you have your problem right there.

Debris will interrupt the electrical current and prevent your lights from working. Carefully clean the dirt and debris away from both the wires and screws.

3. Broken Fuse or Light Bulb

Of course, when you are dealing with lights, you should make sure that the bulbs aren’t broken and that there isn’t a broken fuse.

Check the fuses leading to each light. If there is any damage to them or what looks like a gap in the wire, that means that the fuse has blown out and that you need to replace the fuses.

If the fuses still look like they are in good shape, check how the electricity hits the light bulbs. A sign that you are dealing with burnt-out bulbs is that only some of the lights are not turning on.

You can have the rest of the lights working, but a singular light doesn’t turn on. It also might be the case of a burnt-out light bulb when you turn the lights on, and they flicker for a second before fading to darkness.

When you have a burnt-out light bulb in your running lights, the way to fix it is just by replacing the light.

Replace the light bulb

4. The Pin Heads Got Malformed

Back to the mechanics of your running lights, you should check how the pin heads look after making sure that all the wires and screws are connected properly. A healthy pin head will have a small split in the middle that has a decent-sized gap.

However, this split can get squished together which interrupts the current going through the trailer. To fix this, take a flat-headed screwdriver or even a butter knife and gently pry apart the two sides of the pin. The pin should separate somewhat easily.

If the sides of the pin have gotten messed up to where they can’t be pried apart, you will have to replace the pins.

5. Bad Insulation

Your plugs and wires that are within your 7 pin trailer running lights should have proper insulation. The insulation should be covering the wires completely and there shouldn’t be any gaps or cracks within the insulation.

If your wires don’t have proper insulation, that can lead to water getting to the plug and causing even more problems that will make sure that the lights don’t work. Damaged insulation should be replaced right away.

For those who live in wetter areas and have to keep their trailer in an uncovered area outside, you can put a plastic bag over the plug and secure it by tying it. This gives the plug extra protection against water getting inside.

How to Troubleshoot Your 7 Pin Trailer Running Lights

Depending on the problem that is happening, your trailer might inform you that there is a problem. If there is a problem with the connections, you will receive a warning on your brake controller that there something isn’t connected properly.

From there, you can either bend the connectors back to how they are supposed to be to restart the connection, or you can get a new plug.

Get A New 7 Pin Plug

If the problem isn’t so easily presented to you, you will have to go the long way to diagnose the problem. It is time to get the multi-meter out and check the power, continuity, electricity flow, etc.

Using a process of elimination, your multi-meter should show you what levels are not what they should be and what issue your running lights are having.

When in Doubt, Call a Professional

If you have gone through the entire troubleshooting process, inspected each piece of machinery, and have replaced any damaged materials and your trailer running lights are still not working, then it is time to call a professional.

A professional will be able to diagnose the problem that your trailer lights are having and can think of possible problems that are specific to your trailer model. From there, they will also have the proper tools to fix any screw that isn’t tight or wire that isn’t connected properly.

Professionals know the proper precautions to take when dealing with wire problems. If you are finding that your trailer running lights problem are mostly to do with an issue with the wires, you should call a professional that can safely reconnect them.

Finally, a professional will be able to fix problems quickly and answer any questions that you may have. If you are at a loss for what to do for your trailer, a professional will be able to figure it out.

The 7 Pin Trailer Running Lights Are Color-Coordinated

When you go to check the connection of the wires in your running lights, you will notice that different wires are different colors. Each color stands for something different which is meant to help you figure out what specifically is the problem when a problem arises.

For the traditional SAE wiring, here is what each wire color stands for:

  • Green = Right turn/brake light
  • Yellow = Left turn/brake light
  • Brown = Tail/running lights
  • White = Ground wire
  • Blue = Brake controller output
  • Black = Battery hot lead
  • Purple = Reverse lights

When you know what each wire color stands for, you can see the problem that is happening with your trailer lights by seeing which wire is not connected properly.

For the traditional SAE wiring, you should be looking at the brown wires and making sure that they are properly connected as they are what control the running lights.

Final Thoughts

Technology and machinery can get overwhelming when a problem comes up. You have to spend time figuring out why something isn’t working and then know the right way to fix it. We have listed what to check for when your running lights are flickering or not turning on at all.

However, if you ever find yourself stuck with what to do because you seemed to have tried everything, don’t be afraid to hire a professional for help.

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