Trailer Lights Go Off When I Hit The Brakes

I have a problem with my brakes. My trailer lights go off when I hit the brakes, every time. What can be the reason, and how do I fix it? Read on to find out the answer!

If your trailer lights go off when you hit the brakes, then the main reason for it to happen can be a grounding issue. There can be several reasons for a ground issue, but the main reason behind it is the cause of high amperage. 

For any lights on your trailer to function correctly, they must be grounded properly, and any issue in that can result in the lights malfunctioning. A bad ground connection means that the ground connections are not directly in contact with bare metal like the trailer frame. 

When you press the brake, and the trailer lights are on, the amperage flow increases, which may cause the lights to go off. 


Trailer Lights Go Off When I Hit The Brakes


Running Lights Come On When I Hit The Brakes 

If your running lights come on when you hit the brakes on your vehicle, it is due to some electrical issue resulting in the short-circuiting of the running lights and brakes together. To check whether this is the issue or not, you would need to trace the wirings for your running lights to check if there is any damage.

Another reason your running lights come on when you hit the brakes is a grounding fault. A bad ground connection is a common problem with trailers, and many of the lights malfunctioning are due to this. The main reasons for a grounding fault are replacing your running lights with the wrong bulbs or corroded contacts on the lights. 

Check whether your running lights are the right ones for your vehicle or not, and replace them with the right ones. Check the bulb contacts on your running lights and whether they are properly grounded. 

In case of corroded contacts, clean them properly, and before fitting them, make sure that every light is functioning correctly. 

Electrical shorts can also be the culprit behind your running lights coming on when you hit the brakes. The wiring in your vehicle may have gotten damaged, and the circuits of your running lights and brakes may have shorted together. 

Before taking your whole vehicle apart to check the wiring, consider any recent repairs or changes to your vehicle that might have caused the fault.

In some cases, this problem can be as simple as bad bulbs or a faulty switch. If all the other lights are functioning properly, check whether the bulbs and switches are okay.

Trailer Lights Go Off When I Hit The Brakes 

If your trailer lights go off when you hit the brakes, then a bad ground connection is the most common reason. A grounding fault occurs when all the lights in the trailer are not properly connected to the bare metal frame of the trailer. 

In case of a grounding fault, if the trailer lights are on when you hit the brakes, then the increase in amperage can cause the lights to go off. Make sure that all the bulbs in your trailer are correctly grounded with their contacts touching the bare metal of the trailer frame.

Check for a grounding fault by checking the contacts on the trailer lights. Clean the contacts on the bulbs to remove any corrosion that may have caused bad ground. Make sure that the bulb is functioning before making all the connections. 

If the problem persists, the problem can be due to bad wiring, and it would be better to get your trailer checked out by a mechanic.


Trailer Lights Go Off When I Hit The Brakes


Trailer Lights Go Out When I Hit The Brakes

The main reason behind your trailer lights going out when you hit the brakes is faulty ground connections. In a faulty ground connection, the grounding wire is not in proper contact with the bare metal frame of the trailer. 

If the trailer lights are on and you press the brakes, there will be an increase in the amperage due to faulty ground connections, and that will cause the trailer lights to go out. Corroded contacts on the bulbs in the trailer lights can cause faulty ground. Clean the contacts in the bulbs to ensure that they are in contact with the trailer frame.

Frequently Asked Questions 

Why do I have brake lights but no tail lights on the trailer?

The taillights on your trailer may not work because of faulty bulbs. Check the bulbs in your taillights and if they are faulty, replace them with a new one. Another reason your tail light does not work can be a problematic fuse. Check whether the fuse is intact or not. 

The socket of the tail bulb may have gone bad, or the wiring may have worn out, leading to faulty tail light. A fault in the control switch that triggers the tail light may also be the culprit behind the tail light on your trailer not working.

How do you ground a trailer light?

There are two simple ways to ground a trailer light. You can use either ground as a trailer light by bringing the mounting studs on each light directly in contact with the trailer’s frame. Another way of grounding a trailer light is by connecting a jumper wire from the light to the trailer’s frame. Then you can bring the trailer connector in direct contact with the trailer at the front so that it can use the trailer’s frame as a grounding wire.


Trailer Lights Go Off When I Hit The Brakes


How do you fix the brake light on a trailer?

When you have a troubling brake light on a trailer, check whether the trailer socket and plug are connected properly. They are prone to damage from traveling on rough tracks. Check whether the bulb globe is intact or not. One of the common causes of a faulty brake light in a trailer can be a bad bulb. 

If the bulb globe is fine, then the next place you should check is the light fittings or sockets. Water may have gotten inside the light fittings and resulted in corrosion. Clean it up, and if even then the brake won’t work, then there might be some fault in the wiring. Check whether the bulb is getting enough voltage or not.

How do you wire brakes and lights on a trailer?

Trailers are equipped with a variety of lights and electric brakes, and for these, to function, they are connected to the power source with wirings. Over time these wirings can malfunction with corrosion and damage and need replacements. 

Start by installing a cable with six conductors in the trailer’s frame. Split the wire to bring the green wire to the right side of the trailer and the blue, yellow, and brown wires to the left side of the trailer. Leave the black wire as it is. 

Connect the blue, yellow, and green wires to the trailer brakes, left turn/stop lamp, and right turn/stop lamp. Then connect the brown wires with the taillights and the side marker lights on either side of the trailer. 

Now make the connection of the white-colored wire with the trailer’s frame. Take a five-pin connector and splice all the similar color wires together—apply tape to all the connections you have made.

A Few Final Words

The main reason for trailer lights to go off when you hit the brakes is a ground issue. A faulty ground can increase the amperage when you apply the brakes, resulting in the trailer lights going off. Check for ground faults and clean any corroded contacts on the bulbs.

Thank you for reading, we hope this answered your questions. You might also want to read: What Does it Mean if Reverse Lights Come On When Brakes Applied?

Photo of author

Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

Leave a Comment