What do the Colors on 7-Way Trailer Light Wiring Mean?

Picture this. You have a worn-out wire or some other electrical failing, and some savvy trailer knowledge or clever Googling on your part has taught you that you have 7-way trailer wiring. 

But sadly, every wire is a different color, and you have no idea why. Let’s learn classic color coding for your trailer so you can get your lights shining again with minimal…sparks. 

So grab a wiring kit, and some properly gauged wire, and let’s get to work. 

Two Types of Wiring to Know: SAE Standard or RV Standard

The color coding on your harness is going to vary depending on whether you’ve got a trailer or an RV. Trailer wiring is designed in accord with the practices of the Society of Automotive Engineers, or SAE. 

Color Coding for SAE Standard Trailer Light Wiring

• 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

Color Coding for RV Standard Lights Wiring

• Green: Tail/running lights
• Yellow: Reverse Lights
• Brown: Right turn/brake light
• White: Ground wire
• Blue: Brake cont
• roller output
• Black: Battery hot lead
• Red: Left turn/brake light

What if I don’t know which I have? 

Let’s say you bought a used trailer with tons of unlicensed DIY work. You can always determine which wire is which using a circuit tester. That should help you figure out the intended function of each wire. Also, if you have some non-standard harness, you should definitely choose this option. 

What Size Wiring for a 7-Way Wiring Harness

Generally, the smallest recommended size for a 7-way trailer plug is 16 gauge on turn signals, brake and reverse lights, and the running light wires. But go with 12 gauge for grounding, brake power, and battery hot lead wires. 

More Questions About 7-Way Trailer Light Wiring? 

Call or contact The Trailer Parts Outlet. We sell nation-wide, but our Texas hospitality comes through in every call. We know everything about trailer parts and wiring, so we’re happy to help no matter what snarl of wires you’re faced with, or no matter how many outlets you need replaced.