Understanding Trailer Wiring With The Trailer Parts Outlet

Without wiring, your trailer is just a big box with wheels on it. Wiring is critical to every function on your trailer. If you’re driving down the road at night, your lights need to work. That can’t happen without proper wiring. 

Weather and time can compromise the integrity of your trailer wiring. That’s why you should know how to maintain, repair and replace your wiring when necessary. Check out these trailer wiring kits. 

Common Trailer Wiring Issues

Let’s talk about problems you’re likely to run into with your trailer wiring. 

How can you tell you have a wiring problem? Your lights don’t work, or they are dim. Note that this can also be caused by burnt out bulbs, but corroded wires and poorly grounded wires are common causes. 

Other trailer wiring/lighting hangups you might see:

  • Only one aspect of the lighting like brake or turn signals does not work
  • No lights work
  • Lights worked at start of drive
  • One or more of the lights stays illuminated even though the engine is off
  • Both turn signal lights turn on when you use one of them
  • Reverse lights don’t work
  • The harness works, but not when you connect your trailer

When you are seeing common problems, you should check for the simplest fixes first. If you’re missing a single lighting function, it might be because the harness is not connected. This could be due to a blown fuse or loose set of connectors. It could also be chased by insufficient grounding or a disconnected brake wire.

The 12V power wire isn’t hooked up, or it is not grounded adequately. Perhaps the 12V is not hooked up to the car’s battery. You might have a harness with a factory tow package but a vehicle that does not. 

Next check if the harness wires are not connected. If they seem connected, check for weak connections. Make sure they are grounded, too. 

Testing for Common Trailer Wiring Problems


You’ve got to do a visual check for visual rusting and corrosion. You might need an extra pair of hands (and feet for pedals) to hop in the cab and engage lights while you inspect their performance from the outside. If you are seeing problems, the first thing to try is removing the fuse, and re-installing it. Always try the simple fixes first. After that, test the wiring that goes into the converter box. If that works, check the trailer wiring system. 

Behind the converter box, check the signals that run from the box to the vehicle. The turn signal should be a green and yellow wire. Brake lights for a two-wire vehicle. If any of the light functions don’t have the correct power, check for:

  • Shaky, rattly connectors or wires and missing fuses or relays on a plug-in harness
  • Inconsistent or loose ground connections on a hand-wired harness
  • Wires that are hooked up to the improper places on the truck

Replace with Top-Quality Trailer Wiring Parts & Expert Guidance


The Trailer Parts Outlet offers you top quality wiring parts and expert guidance on trailer wiring questions of all kinds. Feel free to reach out to us for any questions about parts or how to use them you may have. We look forward to hearing from you. 

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