youtubeThe electrical system is one of the key components of any Recreational Vehicle. It literally keeps the lights on and powers key systems within the coach. In this article I will address the basics of the electrical systems (yes, there are multiple electrical systems in an RV) so the reader will gain a better understanding.

RVs generally have three separate electrical systems onboard, and I will discuss them all here. The first is the chassis 12V system. This varies depending on whether the RV is a motorized or towable unit. Let’s examine trailer chassis systems first.

The exterior lights and brakes are powered by the chassis electrical system. The lights are energized by the tow vehicle through the 7-way trailer plug. This means that the exterior trailer lights are not really part of the trailer electrical system at all, as the wiring is isolated from the trailer and fed directly from the tow vehicle. The exterior lights consist of the running, brake, signal, and clearance lights. Should you experience an issue with any of these, you might suspect a bad bulb or connection. RV owners often overlook the importance of a clean and dry 7-way connector. Over time, either or both ends of this connector become dirty and/or wet. Also, the blades (pins) of the connector may loosen up over time so they no longer make a solid connection with the mating plug. It is a good idea to carry electrical contact cleaner and some sandpaper to keep these connectors clean and dry. Sometimes you may have to bend the blades of the trailer end out slightly to make a better connection. Otherwise carry spare bulbs and be prepared to clean the bulb socket(s) if they become dirty, wet, or corroded. It is extremely important to ensure that your exterior trailer lights are always in good working condition.

Trailer brakes also receive their signal from the tow vehicle by way of the brake controller, except for the emergency break-away system. In the case of an unintended separation of the trailer from the tow vehicle, the trailer brakes will fully activate, powered by the trailer battery. This is because a trailer separation will sever the electrical connection between the tow vehicle and the trailer, necessitating an alternate source of DC voltage for the trailer brakes. Therefore, always ensure your trailer battery is in good condition and never tow a trailer without a battery attached.

Trailer House Batteries

For motorhomes, the exterior lights are also an isolated system; part of the chassis system and connected to the chassis battery. As with trailers, they are separate from the house 12VDC system. Ensuring your exterior clearance/marker, running, signal, reverse, and brake lights are in good working condition should be part of every pre-trip inspection.

The second onboard electrical system is the low voltage 12VDC system that power most interior lights (plus exterior “scare”, awning, and porch lights), appliance control boards, 12V fans, etc. This power comes from the house batteries, converter, solar panels, and/or inverter/charger. 12VDC battery power is what allows you to have your lights and other 12V appliances operate while driving or dry camping. Failure of these systems to operate. 12VDC system or component failures are rarely serious and can generally be traced to a battery problem, a faulty connection or wiring, blown bulbs, or fuses.

Converter 12V Fuses

GFCI Receptacle

Finally, we have the 120VAC power system. This is an isolated system, which is the same as the power in your house. It allows for the operation of your rooftop Air Conditioners, washer/dryer, 120VAC energy source for your fridge and water heater, 120VAC wall receptacles, etc. This energy comes from shore power, generator, or inverter. Faulty AC power can generally be traced to bad shore power, generator, or inverter, faulty wiring, or a tripped breaker.

Inverter Charger

Of course, there can be other sources of failure for any of the three separate power sources listed in this article, but troubleshooting is outside the scope of this article. Hopefully this article has helped the reader understand the three distinct electrical systems within your RV.

Steve Froese
Author: Steve FroeseEmail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Steve Froese is a Licensed Professional Engineer in British Columbia, as well as an Interprovincial Red Seal RV Technician, which is equivalent to a Master Certified RV Technician in the USA. Steve was a personal friend and colleague of the late Gary Bunzer (“the RV Doctor”), and works closely with FMCA as the monthly “Tech Talk” columnist, as well as being a member of the Technical Advisory and Education Committees. Steve and his family are lifelong and avid RVers, mostly in the Pacific Northwest.


0 #1 Larry Hinton 2022-04-30 17:51
I have been using Dow Corning DC-4 insulation Compound for electrical connections which may be subjected to moisture. The silicon displaces the moisture and keeps the contacts clean from corrosion. The main subjects are trailer to tow connector, all external light bulbs (if still using incandescent lamps)

The product is now known as DuPont MolyKote 4.

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