But in addition to the 110 volt electrical supply there may also be lights, fans, refrigerator, or other electrical devices which use a 12 volt supply like that of a car or truck.
This 12volt system powers the refrigerator to keep food cold while the RV or camper trailer is being transported from place to place. The same goes for the lights and fans. It also keeps the on-board batteries fully charged. This 12 volt DC system relies on the 110 volt AC electrical power supply for the needed amperage.
110 volt power-- > converter-- > 12 volt power-- > 12 volt breaker box -- > refrigerator or lights
As in a home, the 12 volt system has its own set of breakers to control each 12 volt circuit. The lights, fans, or refrigerator may all be on their own circuit depending on the amperage required. If the converter is supplying 12 volts to the breaker panel and the breakers test positive for voltage this leaves the wiring or the particular appliance at fault.
Understanding the 110 Volt System
110 Volt Systems
The 110 volt outlets used in some 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 and end to loose connections. Since some of the walls are so thin a smaller receptacle box may be required for the outlet to fit flush in the walls.
Ground fault interrupter outlets are another common cause of electrical problems. These are located in places where a possibility exists of someone touching them with wet hands. They automatically break the circuit when moisture comes in contact with the outlet to prevent shock to the person touching them. A simple reset button must be pressed for the circuit to once again be completed. On occasion they will need to be replaced or the other outlets on the line will not work either. Pay close attention to the instructions when replacing these GFIs.
For the sake of an example let’s say that we are dry camping and our 12-volt water pump quits working.
I am convinced that just about anybody is capable of troubleshooting a 12-VDC problem, and in many cases repairing the problem without it ruining your camping trip. For starters you will need a couple of simple tools to assist you in troubleshooting your RV’s 12-volt electrical system.
1). An inexpensive 12-volt test light.
2). A multi-meter that can test for DC power.
Both of these are available at local auto parts stores. You should also keep some electrical tape, various size wire nuts, 12-volt light bulbs and 12-volt fuses on hand. Check the amperage of the fuses used in the power distribution box and keep an assortment. If you’re aware of any inline fuses used on any of the 12-volt devices keep these on hand too.
Now, try to determine the last time the water pump actually worked. Did you leave the RV for a period of time with the pump on? Is there water in the fresh water holding tank? Were you working on or around something else that could have affected the operation of the water pump? Try to think of all possible scenarios. Something might jar your memory resulting in a quick fix to the problem.
If not, the first step is to verify that the coach battery or batteries are charged enough to supply power to these 12-volt items. There are a couple of ways to perform a quick test on the coach batteries. You can use the monitor panel to check the condition of the coach batteries. To get an accurate reading make sure the RV is not plugged into electricity and turn on a couple of overhead lights to place a small load on the battery. Check the reading at the monitor panel. (If you check the reading at the monitor panel when the RV is plugged in to electricity it will give you fully charged reading) A more accurate method is to test the battery with a multi-meter. Set the meter to read 12-VDC and place the negative test probe on the negative battery terminal and the positive test probe on the positive battery terminal . A fully charged battery will read in the range of 12.6 to 12.7 volts. If it reads less than 12-volts it is below a 50% state of charge and will need to be charged.
IF THE BATTERY IS FULLY CHARGED the next step is to make sure that any battery disconnect switch for the coach battery is turned on. If the battery disconnect switch is on, verify that other 12-volt devices in the RV are operating properly. If there is 12-volt power to the interior of the RV you need to check the fuse for the water pump in the power distribution center. Determine which fuse is for the water pump (fuses are normally labeled) and find a suitable ground for the 12-volt test light. Test both sides of the fuse for 12-volt power. If the test light only lights on one side of the fuse replace it with the proper size fuse and try the water pump again. If there was power at both sides of the fuse check for 12-volts at the water pump switch. If there is voltage, and the switch is operating properly check the water pump wiring for an inline fuse.
Find a good ground for the 12-volt test light and probe the wire on both sides of the fuse. If there is only power on one side of the fuse replace it with the proper size fuse and test the pump again. If there is power on both sides of the fuse check the water pump wiring connections at the wire nuts. It’s possible for connections to come loose due to excessive vibration. Correct any loose connections and try the pump again. If the pump still doesn’t work feel the motor to see if it is hot to the touch. If the motor is hot, a thermal breaker may have been triggered. Allow the pump time to cool off and see if it re-sets itself.
If you complete all of these tests and there is 12-volt DC power coming to the water pump motor, and it still doesn’t come on, chances are the water pump is bad and it will need to be replaced.
Troubleshooting a 12-volt electrical problem in your RV is not that difficult. Follow the logical path of the device you are troubleshooting and see if you can determine where the problem is. It might be possible for you to save your well deserved vacation, some money and a trip to the RV dealership too.
Note: If you don’t feel comfortable performing your own maintenance or troubleshooting the 12-volt electrical system, take your RV to a reputable repair center to have it checked out and repaired.
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