Robin and Paul
270 E Jackson Street (US RT 6)
Seneca, IL 61360
815/357-3292, FAX 815/357-9920

Email Paul@needatrailer.com
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I sell many 7 way trailer plugs and cords, click here to see them
To confuse matters worse, TYPICAL trailer wire colors are below. IF (and I say IF) your trailer uses the standard wire colors, then you will need to match the FUNCTION, not the color!



White = Ground 12 volt Neg.
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)

Trailers normally dont have back up lights, if they do, there is not "standard" color--  The reverse light is the CENTER pin on the plug!)


(So, For example, the red "plug" wire will connect to the Yellow "trailer" wire = Left stop/turn)
All you ever wanted to know about 7 way trailer plugs!
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, preferablably 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)




  • 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......



  • 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
I sell many 7 way trailer plugs and cords, click here to see them

Wire Color by Vehicle Manufacturer

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
Wiring Code 7 way Car End
# Color Gage Circuit Function connector interior
1 white 10 common ground [7 way connector]
2 blue 12 electric brake
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/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.
Wiring Code 7 way Trailer End
# Color Gage Circuit Function connector interior
1 white 10 common ground [7 way connector]
2 blue 12 electric brake
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/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.
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. -