How to Troubleshoot and Repair a Camper or Travel Trailer Electrical System
RV electrical systems sometimes fail. They are meant to last for years, but when we bounce along the road and expose them to the elements, connections can break or rust. Keeping your electrical systems in good and safe working order ensures a trouble-free camping trip with no sudden power outages to ruin the trip. You can repair many problems easily if you understand how the system works.
RVs Have Two Electrical Systems
When you start looking for your issue, you should know that most RV’s and camper trailers have two electrical systems: a 110-volt AC system like that in your home, and a 12-volt DC system, supplied by batteries like those in an ordinary car or truck. The 12-volt system generally powers the lights, fans, slides, and other electrical devices. It often controls the thermostat of the refrigerator, air conditioner, and water heater.
While the RV or camper-trailer is moving from place to place, the 12-volt DC system powers the RV refrigerator and keeps food cold, and runs the lights and fans. When the RV stops at a campground, it plugs into an 110-volt or 120-volt AC electrical power supply.
While you are driving, the 12-volt system keeps the on-board batteries fully charged. This system relies on the 110-volt AC electrical power supply for amperage.
It is possible to pull a 12-volt power supply from either the RV's or camper trailer's 12-volt system or the 110-volt campsite power supply. The power converter steps down the 110-volt supply to 12 volts before it goes to a particular appliance.
When there is an interruption in the 110-volt AC supply, most RV systems will switch from the 110-volt AC back to the 12-volt DC supply automatically.
Is Your Problem With the 12-Volt or the 110-Volt System?
When you diagnose electrical problems, you treat these two systems (12-volt and 110-volt) independently from each other, except when they interact through the RV’s converter.
12-volt appliances can include slides, lights, fans, or the thermostats of other appliances (air conditioner, hot water heater, refrigerator).
Your “plugs” in the RV’s bathroom and kitchen, your microwave, and many modern appliances are 110-volt. If they malfunction, the issue may well be in the 110-volt system.
But remember that many 110-volt appliances have thermostats that are 12-volt. If your air conditioner, water heater, or fridge refuse to go on or off, you may have a 12-volt problem, not a 110-volt problem.
The Parts of the 12-Volt System
Consider the train of connections from the power to the appliance: problems may appear at each step.
When you are plugged into shore power (your campsite or home electrical system), electricity flows to your 12-volt appliance as follows:
110-volt power —> converter —> 12-volt power—> 12-volt breaker box —> appliance
When you are driving or dry camping, the process is:
coach battery or batteries —>12-volt power —> 12-volt breaker box —> appliance
The 12-volt system has its own set of breakers to control each circuit. The lights, fans, or refrigerator may each be on their own circuits, depending on the amperage required.
Use your multimeter to find the voltage in different parts of the 12-volt system. If the converter (or the battery) is supplying 12 volts to the breaker panel, and the breakers test positive for voltage, then you can assume the wiring or the particular appliance at fault,
Troubleshooting Common 12-Volt Problems
Here are some common issues and problems you should try to eliminate early on in your investigation.
- Could your battery be the problem? One very common issue is a bad ground for the battery. Make sure the battery cable’s negative end is clean and firmly attached (grounded) to the steel frame of the RV. If it’s corroded or loose it can cause all kinds of problems.
- Another common issue in the 12-volt system is a battery that is low on water. Make sure the battery has enough fluid. If adding some distilled water to the battery doesn’t fix the problem, the battery may be bad and need to be replaced.
- Could your converter be the problem? To find the converter, follow the positive battery cable. The converter is likely near the power panel containing the fuses or breakers for the 12-volt DC system. It may be located in an outer access panel, or there may be an inside access panel you need to remove.
- Make sure, of course, that the converter is connected; if it there is a breaker or fuse on the positive cable between the battery and the converter, make sure the breaker has not tripped. Not all campers have this circuit breaker or fuse.
- If the converter is good, it should supply at least 13 volts to the battery when the converter breaker is on. You can test the converter by turning the converter’s breaker off or removing its fuse and connecting a good strong battery charger (not a trickle type) to the battery posts or the place where the battery should be. If the power from the charger causes the appliances to work, then the converter is bad. This article has more about what can go wrong with converters and when you may need to replace them.
- If you don't know where to look for a problem in the 12-volt system (lights, slides, thermostats, fans, etc.), you can use your multimeter to check the breakers and fixtures. Start with the 12-volt DC breaker box. Check each breaker at the point where the wires lead away from the breaker to the lights, fans, etc. If you find the breakers are working properly, check each non-working light to see if power is getting to them. A bad connection at one of the lights can prevent the electrical current from continuing on to other fixtures. A broken connection is more easily found if you use the OHM setting on the multimeter.
- "Bad grounds" may occur at other places in the system besides the battery, if a circuit that is supposed to be grounded (connected to the frame) has worked loose.
Troubleshooting Common 110-Volt Problems
- Some 110-volt outlets used in RVs and camper trailers are prone to shorts because of the way they are installed. Some are merely clipped onto the wiring by cutting into the wires. These types are notorious for not working correctly. Replace these types of outlets with standard house types to put an end to loose connections. Since some RV walls are so thin, a smaller receptacle box may be required for the outlet to fit flush in the walls.
- Ground fault interrupter (GFI) outlets are another common cause of electrical problems. These are located in places (often kitchens and bathrooms) where a possibility exists of someone touching them with wet hands. They automatically break the circuit when wet, to prevent shock to the person touching them. They have a reset button which you can press to complete the circuit again. They may control more than one outlet or appliance. GFIs often go bad after a few years and may need to be replaced. Pay close attention to the instructions when replacing these GFIs.
- If you don't know what circuit is causing the GFI to trip, turn off all the breakers in the 110-volt breaker box except the main breaker, reset the GFI, and then turn on the 110-volt breakers one at a time until you find the one that causes the GFI to trip.
- In older RVs and camper trailers you may still find fuses instead of circuit breakers. These older fuse systems may not provide enough amperage to handle a modern microwave or a combination of other high-amp appliances without blowing a fuse or kicking a breaker. Simply replacing the fuse or breaker with a higher-amp substitute may be all that’s required. Replacement of the entire breaker box may be the only option remaining if this doesn’t solve the problem.
- If fuses keep blowing, try removing all the fuses except the main fuse and replacing the other fuses one at a time until you find the one that blows the main fuse. This test assumes the main fuse is good.
- The newer RVs and camper trailers may have two RV A/C rooftop units which require more amperage than the older models to operate. They may not be able to run without kicking off the standard 30-amp power supply used by many campgrounds. Fortunately, many campgrounds and RV parks now provide 50-amp service for these types of units. When making reservations or checking in, be sure to ask about the availability of a 50-amp hook-up if you own a unit with multiple A/C units.
- It's good to know that there should be a breaker in the 110-120 volt AC panel marked "converter" that provides electricity to the converter.
Troubleshooting Breaker Boxes (12-volt or 110-volt)
The 12-volt and 110-volt breaker panels are usually near where the 110-volt power "shore connection" exits the camper.
- If breakers keep going off, try turning off all breakers in a panel except the main breaker. Then turn the other breakers back on one at a time to see which circuit is causing the breaker to "trip" or shut off.
- Breakers themselves can wear out and go bad after being tripped too many times. They may refuse to stay closed, especially when warm, and may need to be replaced.
You Can Learn to Do it Yourself
Most problems can be repaired easily if you understand how the system works. RV electrical manuals along with a few inexpensive tools are well worth the cost of their purchase.
If you are completely confused by electrical wiring there are also some very good basic books to start you off. It isn’t hard to check electrical circuits, switches or outlets with an inexpensive voltmeter.
Caution: Make Sure the Power is Off
Just remember, before touching any wires, be sure the power to that particular circuit is off. If in doubt, turn off the main breaker, or unplug the RV or camper trailer from the power supply.
Essential Tools and Resources
- If you are not familiar with electrical wiring or troubleshooting electrical systems, I would recommend to any novice and experienced electrician alike. This good book will be an enormous aid to understanding RV electrical systems. RV Electrical Systems: A Basic Guide to Troubleshooting, Repairing and Improvement
- A must for tracking down electrical problems is a voltage meter. This handy tool will allow you to check the circuits for continuity and for the correct voltage required for each breaker. A simple test light can also be used but will not test for broken circuits caused by bad wiring or other electrical problems. A voltage meter can be used for home electrical problems too. is inexpensive but will do the job. This Greenlee model
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.