Fixing Right Or Left Turn Signals Not Working On a Trailer

Letting drivers around you know your intentions is part of being a safe and responsible driver. But sometimes, that communication cannot be maintained. When the turn signals break or have a bad connection other drivers are left guessing at what you will do.

In some cases, the 7-pin connector may not be connecting properly or some corrosion got on the connection. Either way, this is one of the sources for why your turn signal does not work. Check your connector to see that everything is working as it should.

To learn more about this problem, just continue to read our article. It has the information you want to know about so you can solve your problem a little faster than normal. Take a few minutes to see how this information can help you fix your turn signals.

Turn Signals Not Working on The Trailer


There are numerous sources for this problem. There always is when electricity is involved. The time-consuming part is tracking down the correct source. But you should use this time to clean up potential problems as you hunt for the source.

By that we mean, that if the connections in the trailer pin are not the source, make sure it doesn’t become a problem and clean up the connections before moving on. Then test them to make sure each pin has power to it.

The trailer pin connector may be the source so go to it first. Test the pins for power, and look for corrosion. There may be a loose wire to one of the pins that are cutting off your turn signals. Or a loose or bad connection.

Fix that and you should be okay. But the problem may be in the lights and they may have burned out, have a loose wire, or a short somewhere. It will take time but eventually, you will get to the correct source.

How do You Troubleshoot a Turn Signal on a Trailer?

The fastest way to test your turn signals would be to bring in another vehicle and connect it to your trailer. Or connect your vehicle to another trailer. This will let you know if there is a problem with the wiring harness or not.

If the turn signals work with the new vehicle, then the problem is with your vehicle’s connection. If the new trailer’s lights work when connected to your vehicle, then the problem should lie on your trailer’s side of the connection.

If using different vehicles and trailers is not an option, then you should be testing your wire harness with a multi-meter or circuit tester. If you do not get a signal with the ester, your wire harness should be bad.

If you do get a signal, then the problem lies with the trailer and it could be a loose wire/connection, a bad wire, lights have burned out, and so on. Pinpointing the problem like this helps eliminate possibilities and speeds up your repair time.

What Would Cause Both Turn Signals To Stop Working?


The first source for this problem could be very simple. The bulbs, whether standard or LED, could have burned out. Moisture may have found its way into the light and ruined the bulbs.

Or that same moisture may have corroded the connections, damaged the wires there, and turned off the lights. If that is not the problem, then you should trace the wires back to the wire harness. You are looking for any breaks in the wire or other damage that may cut off the electricity.

Finally, you should examine the wire harness and see what condition it is in. If it is bad, you need to replace it. But if it is just a loose connection, then tighten the connection and make sure all the pins fit securely together.

Also, you should check to see if you have a ground problem. If the ground wire Is not connected properly, that will turn your signals off and not let them function. Check all your ground wires and not just the one at your wire harness.

Is There a Fuse For Trailer Turn Signals?

This may be a car brand-specific problem and not every car from that brand may have a fuse for trailer turn signals. Usually, though, there is a fuse for the trailer turn signals. You would have to check each fuse out to see if you do or not.

The problem comes in, especially for owners of the 2015 Transit 150, is that the fuse for the trailer turn signals may not be labeled. The other problem is that you may only be able to buy that fuse from a Ford dealer.

Some generic ones do not fit into the space. The second problem is its location. It could be in the power distribution box next to the engine or it could be in the interior fuse box. If the fuse is bad, you just replace it. You will be able to see if the fuse is bad.

If the relay is bad, you should be able to hear a clicking noise but you won’t see anything wrong. The fuse won’t always be the problem but check it anyways just to eliminate it.

The Trailer Turn Signal Not Working When The Lights Are On


If by lights, it is meant, running lights, then the source of this problem is not usually in the wire harness. Although it could be. Generally, when the running lights are on and the turn signals are not working, then there is a problem with the ground wire.

The connection may be weak and only lets enough power through to let the running lights work. To fix this you have to track down the ground connection and see if it is securely connected. If not, then make it that way.

If the ground connection is good, then the problem may be that your wire harness is not rated for trailer lights. If that is the case, you have to change your wire harness and use one that is rated for trailer lights.

Those are the main two sources of this problem. There may be a side issue that is hard to find and a good car electrician should be able to track those side issues down and correct them.

With electrical connections, the problems are usually very straight forward and you have limited possibilities. Check those possibilities and your problem will be solved with the right repair.

The Right Turn Signal Not Working On a Trailer

The first step in tracking down the source of this problem is unhooking the trailer from your tow vehicle. Then you get a circuit tester out and test the wire harness on the tow vehicle side.

If power is not getting to the turn signal pin, then a fuse may be blown or it is missing. If either of these is the case, then replace the missing or broken fuse. If power is getting to the trailer turn signal pin, then the issue could be a loose ground wire.

Don’t replace the whole light if this is the problem. This is a wiring problem and not a turn signal one. Check for loose connections, corrosion, etc., and repair according to the problem.

If the wire that operates the turn signal is bad, you will have to replace it. In this case, it is a green-colored wire. The brown wire is for the running lights. Check your wires for damaged, loose connections before turning to the light bulbs. Sometimes, it is just a light bulb that has burned out.

Left Turn Signal Not Working on a Trailer


Basically, everything that was said for the right turn light will apply to this light. The only difference being is that the left turn signal is operated by a yellow wire and not a green or a brown one.

You will see a brown wire with the yellow wire but that brown wire is for the running lights only. That is if the trailer is wired correctly and to color code. If you bought a used trailer from someone who liked to do his own work, the color wire code may not have been followed.

Stay alert for those changes and make sure you get the right wire to the turn signals. Again, sometimes those bulbs just burn out and you only need a replacement.

It is your choice to check the bulb or go to the wiring issues first before checking the other parts.

Some Final Words

When it comes to electrical devices like turn signals, your source issues are limited. There is either power going to the signals or there is not. Or there may be a loose connection or either the light or the wire harness has gone bad.

The trouble comes in when you are not sure and you have to spend a lot of time tracking down the source. Once you find it, the fix is very easy and your problem will be solved.

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