| Wiring Code | ||
|---|---|---|
| Common 7 way Connector | Function | Usual Trailer Wire |
| White Wire | Ground | White Wire |
| Red Wire | Left Turn and Brake | Yellow Wire |
| Brown Wire | Right Turn and Brake | Green Wire |
| Green Wire | Tail Lights | Brown Wire |
| Blue Wire | Brake Power | Blue Wire |
| Black Wire | 12 volt (hot lead) | Black Wire |
| Yellow Wire | Aux. | - |
White = Ground 12 volt Negative
Black = Aux 12 volt Pos. (sometimes not used... sometime red... sometimes if you have no white on trailer, this may be the ground wire)
Green = Right Stop/Turn
Yellow = Left Stop/Turn
Brown = Tail Marker lights
Blue = Electric Brakes (Sometimes this will be black wire in a double wire cord with the white)
(So, For example, the red "plug" wire will connect to the Yellow "trailer" wire = Left stop/turn)
Trailers normally don't have back up lights, if they do, there is not "standard" color-- The reverse light is the CENTER pin on the plug!)
| # | Color | Gauge | Circuit Function | Truck/Car End Connector Interior |
| 1 | White | 10 | Common Ground |
 |
| 2 | Blue | 12 | Electric Brakes | |
| 3 | Green | 14 | Tail/Running Lights | |
| 4 | Black | 10 | Battery Charge (+) | |
| 5 | Red | 14 | Left Turn/Stop | |
| 6 | Brown | 14 | Right Turn/Stop | |
| 7 | Yellow | 14 | Auxiliary/ Backup | |
| NOTE: #7 is the center terminal and currently is most commonly used for backup lights. | ||||
| # | Color | Gauge | Circuit Function | Trailer Connector Interior |
| 1 | White | 10 | Common Ground |
 |
| 2 | Blue | 12 | Electric Brakes | |
| 3 | Green | 14 | Tail/Running Lights | |
| 4 | Black | 10 | Battery Charge (+) | |
| 5 | Red | 14 | Left Turn/Stop | |
| 6 | Brown | 14 | Right Turn/Stop | |
| 7 | Yellow | 14 | Auxiliary/ Backup | |
| NOTE: #7 is the center terminal and currently is most commonly used for backup lights. | ||||
| Dual Purpose Bulb System | ||||||||
|---|---|---|---|---|---|---|---|---|
| Wire Function | Wire Color | GMC | Ford | Chrysler | Jeep | Toyota | Honda | Mazda |
| Right Turn & Brake Lights | Green | Green | Orange w/ Blue Stripe | Brown | Brown | Green w/ Yellow Stripe | Green w/ Yellow Stripe | Green w/ Yellow Stripe |
| Left Turn & Brake Lights | Yellow | Yellow | Lt Green Orange Stripe | Dk Green | Grey w/ Black Stripe | Green w/ Black Stripe | Green w/ Blue Stripe | Black Stripe |
| Tail Lights | Brown | Brown | Brown | Black w/ Yellow Stripe or Black | Blue | Red w/ Green | Red w/ Black Stripe | Green or Black Stripe |
| Ground | White | Black | Black or Grey | Black | Black & Black | Black or White | Black | Black |
| Single Purpose Bulb System | ||||||||
| Brake Lights | Use Converter | Pink or Lt Blue | Red w/ Green Stripe | White | Blue w/ Black Stripe | Green w/ Red or White Stripe | Green w/ White Stripe | Green or Green w/ Red Stripe |
| Backup Lights | Red | Lt Green | Black w/ Pink | Violet | Brown | - | - | - |
| Electric Trailer Brakes | Connect To Blue Wire From Brake Controller | |||||||
7 Way Wiring Diagram (Click for a Bigger Image)
Other Notes About Trailer Wiring:
You can not have too many grounds! Make sure your ground wire (typically white) is securely attached to the frame on both the truck and trailer side, preferably at more than one location on the frame! The ground wire should be large enough to handle all the load, do not depend on grounding through the ball.
Wire Size:
- 16 Ga, 10amps, Lights only
- 14 Ga, 15 amps, Lights and up to 2 axle brakes (4 wheels, max)
- 12 Ga, 20 amps, 3 axle brake wire, typical ground wire size, also, 12 volt AUX feed
- 10 Ga. 30 amps, for those extreme applications, bigger trailers or campers with big loads.
Typically if you have 2 or more brake axles, lots of lights, and use the 12 volt AUX feed to power items, or charge a battery.... (add up your load, what could items run at once- example, all lights + brakes)
Remember, Trailers DO NOT have "Brake" lights, they have only left and right turn. It's just when they are "on but not flashing", it is assumed to mean brake light. Still only one light on each side, so if your turn signals work, but not the brakes lights, it is your truck, not the trailer.... the "brake light" works on the trailer, the truck just tells then when to flash or not.
If your brake lights work, OR your marker lights work, but everything quits when you turn on both at the same time, your trailer is not grounded to the truck. Period. (at night, when you step on the brakes, all the trailer lights go out) ---see line one, above
Trailer Plug Maintenance
Put grease on your trailer plug, (just plain damn grease). That green junk is copper oxide. It happens when you combine oxygen with copper. All you need is a thin layer of anything (and grease is cheap and sticky) to keep the oxygen (from the air or water) from getting to the copper. The rubber caps just hold the water in...
Still Have More Questions? Email Paul!