Tip & How-To about GMC Blazer

Trailer Wiring Cheat Sheet

Hello all,

For those of you that have or occasionally borrow trailers and look at the wiring plugs with disdain (I mean face it they don't make sense, ground is white, +12vdc is black, etc), this is for you.

The following are the accepted standards for different trailer types.
The different plugs and connectors used are marked with either a number or letters. Having the functions of each in advance can save a lot of trial and error when troubleshooting..

Plug Types/Application
7 Way - RV Trailers, Horse and Utility Trailers
6 Way - Horse, Stock and Utility
4 Way - Utility Trailers

Columns are: Color, Function, Mark on the plug.

Seven wire Trailer plugs:

Horse, stock or utility trailers:

White = Ground - 1
Blue = Electric Brakes - 2
Brown = Tail and clearance lights - 3
Black = Battery, aux power - 4
Yellow = Left turn/Brake - 5
Green = Right turn Brake - 6
Orange or Purple (not both) = Auxilliary or Reverse - 7

Recreational Vehicle:
White = Ground - 1
Blue = Electric Brakes - 2
Green = Tail and clearance lights - 3
Black = Battery, aux power - 4
Red = Left turn/Brake - 5
Brown = Right turn Brake - 6
Yellow = Auxilliary or Reverse - 7


Six wire trailer plugs:

Horse, stock or utility trailers:
White = Ground - GD
Yellow = Left turn/Brake -LT
Green = Right turn Brake -RT
Brown = Tail and clearance lights - TM
Red or Black (not both) = Battery, aux power - A
Blue = Electric Brakes - S

Recreational Vehicle: (color, use, plug mark)
White = Ground - GD
Brown = Right turn Brake - RT
Green = Tail and clearance lights -TM
Black = Battery, aux power - A
Red = Left turn/Brake - LT
Blue = Electric Brakes - S


Four wire plugs:
White = Ground
Yellow = Left turn/Brake
Green = Right turn Brake
Brown = Tail and clearance lights


Ground should be 10ga.
Others 14 ga

Best regards
Mike

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