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Beginners Guide to RV Wiring

General Trouble Shooting

This guide is not meant to be a full training manual on all aspects of RV wiring, rather it is designed to help the average do-it-yourselfer find and repair the most common wiring problems. If you are not comfortable using tools or if the problem is found to be in the wiring harness of the tow vehicle, it is recommended that you seek the help of a professional.

Most problems with RV wiring originates in the tow vehicle socket and/or the trailer plug. With all the rain water, road salt, and grime thrown up by the tires, these components are subjected to the worst conditions for an electrical connection.

First, check the inside connections of the tow vehicle socket for corrosion, broken wires or other obvious problems.

Then inspect the trailer plug for the same conditions. Any deterioration of the terminals or the wires themselves should be repaired now. It is often more economical (and less stressful) to replace the entire plug/socket and make any needed repairs to the wires at this point. Often the problem is solved before delving deeper into the wiring maze.

Wiring the RV Trailer Plug

It's not as hard as you think!


Tools you will need ...

Wiring the 4 pole utility trailer plug

Wiring the 6 pole horse trailer plug

Wiring the 7 pole RV Tow Vehicle Socket

Toad wiring made easy

Emergency Flasher for your RV


Wiring the 4 pole utility trailer plug

4 pole wiring diagram

Pin locations for the flat four pole plug

The four pole plug is a simple connection for a boat or utility trailer and is used for lighting only. It is a flat connection with four wires.

Terminal Wire Color Function Location - Truck Location Trailer
1 White Ground uncovered pin covered pin
2 Brown Running Lights 1st covered pin 1st uncovered pin
3 Yellow Left turn/brake light 2nd covered pin 2nd uncovered pin
4 Green Right turn/brake light 3rd covered pin 3rd uncovered pin

Wiring the 6 pole horse trailer plug

6 pole plug
Pin locations for the 6 pole plug
ASME wiring color code
Terminal Marking Wire Color Function
GD White Ground
TM Brown Running Lights
LT Yellow Left turn/brake light
RT Green Right turn/brake light
ST Blue Brake Control
Aux Black Power

Pin locations for the 6 pole plug
RV wiring color code
Terminal Marking Wire Color Function
GD White Ground
TM Green Running Lights
LT Red Left turn/brake light
RT Brown Right turn/brake light
ST Blue Brake Control
Aux Black Power

Wiring the 7 pole RV Vehicle Socket

There are two wiring codes for different 7 pole plug sets.

Most RV's use the RV wiring code for the type of plug/socket
that has 6 flat contacts surrounding the center round pin.

Semi's and other commercial trailers use the ASME
(American Society of Mechanical Engineers) type of 7-pole plug set.
This plug has 6 round contacts surrounding the center pin.
The wiring color code for this plug is not the same as the
RV 7 pole plug described below, and will be included at a future time.

View looking into the front (contact) end of tow vehicle socket.
7 pole RV plug/socket.
Terminal Wire Color Function Location - Truck socket Location Trailer plug
1 White Ground 7:00 o'clock 5:00 o'clock
2 Blue Brakes 5:00 o'clock 7:00 o'clock
3 Green Running 10:00 o'clock 2:00 o'clock
4 Black Power 2:00 o'clock 10:00 o'clock
5 Red LT & Stop 9:00 o'clock 3:00 o'clock
6 Brown RT & Stop 3:00 o'clock 9:00 o'clock
7 Yellow Aux or BU Center Center

Toad Wiring Made Easy

Note: a "toad" is a small vehicle towed behind a motorhome.

Instead of hooking in to the cars existing system you can simply mount a very nice set of lights under the rear bumper, below the existing light array, and run separate wires under the toad chassis.

toad lights

This method would eliminate the neccessity of installing diodes into the toad lighting circuits to prevent feedback problems. A four pole connector at the front of the toad connects the add-on lights to the motor homes circuits.

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