How to Wire a Travel Trailer for Electric

by John Cagney Nash
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coach, trailer image by Greg Pickens from

Travel trailers customarily have three sets of wiring installed. There are the 12-volt circuits which run the mechanical and exterior lighting functions of the trailer, controlled by the trailer hitch harness and the tow vehicle. There are the interior 12-volt circuits for lighting and outlets which are powered by a deep cycle battery. And finally there are interior 120-volt circuits for appliances and outlets powered by a shore connection to a grid. Wiring a travel trailer will usually require the installation of at least the mechanical and exterior lighting circuits and the 12-volt interior circuits, and usually the 120-volt circuits also.

Step 1

Install the harness which connects the various exterior lights, the electric brakes (if fitted) and the 12-volt charge to the on-board batteries. Run wires to both tail lights, both stop/blinker lights, all running lights, the tag illuminator, the electric brakes, the on-board deep cycle and break-away batteries and a ground to a chassis rail.

Step 2

Observe the conventional color-coding and American Wire Gauge, or AWG, sizing of the exterior light wires. The coding is white to ground, 10-gauge; blue to electric brakes, 12-gauge; brown to tail lights/running lights/license plate illuminator, 14-gauge; black or black/red to battery charge/12 volt supply, 10-gauge; yellow to left turn/brake light, 14-gauge; green to right turn/brake light, 14-gauge and purple to backup light, 14-gauge.

Step 3

Plan then install the 12-volt interior circuits for lighting and outlets. Run an eight-gauge red or black wire from the positive terminal of the deep cycle battery to a fuse board, then individually fuse supplies to light switches and lights, outlets and fixed appliances. The correct fuse sizes can be found in instruction manuals or on information stickers attached to each appliance. Use white color-coded wire for all runs to ground. Store the plan with all the other documents relevant to the trailer.

Step 4

Determine the level of provision required from a 120-volt installation, then draw a plan marking the exact locations of all wires to be installed. Use a six-gauge or heavier cord sleeved in UV- and frost-resistant insulation as a shore connection, and connect it directly to an onboard household circuit breaker board.

Step 5

Run separate circuits to lighting, to outlets in the living area of the trailer, to Ground Fault Circuit Interrupter outlets in the bathroom and galley and to heavy-demand appliances such as cookers and air conditioners. Install a converter charger to recharge the 12-volt deep cycle battery when the shore power cord is plugged into a grid. Store the plan with all the other documents relevant to the trailer.

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