In part 3 of this four-part series regarding your RV electrical system, we will be discussing system troubleshooting. In case you missed Part 1 and Part 2, be sure to check them out too.
Given the importance of the RV electrical system, and the fact that many electrical problems can be fixed with a little knowledge and the right equipment, I highly recommend all RV owners invest in a digital multi-tester. They are inexpensive and invaluable when tracing power problems. If you don’t have a meter, they can be purchased from a local home improvement or electronics store or found online. If you don’t know how to use one, a wealth of information can be found on the internet.
If you have problems with a 12V component in the RV, the first thing to check is the fuse protecting that circuit. Most fuses are mounted together in the power distribution center. It is important that RV owners know where the fuses and breaker panel is located. It is sometimes difficult to tell with the naked eye whether a fuse is blown, so it is always a good idea to “ohm” out a fuse with a multi-tester to determine if it is blown. Some 12V systems have inline fuses, so if you can’t find the fuse for a given circuit in the fuse panel, search for an inline fuse. 
Inline fuses are required to be installed within 18 inches of the batteries, so you can often find inline fuses near the batteries.
Make sure you locate a fuse for any 12V system you are troubleshooting, as that is the most common cause of failure. Be aware that a single fuse may protect more than one device. If the fuse isn’t blown (be sure to check it with a meter), look for loose or broken wires. This can be difficult, but once again, a meter comes in very handy to probe the voltage along the wire. Since the wiring is often hidden behind walls and other structural members, access will be limited. The best thing to do is check for voltage at the effected device, such as the water pump. If you have voltage there, but the device isn’t working, it is likely the device has failed. If you don’t have voltage there, check for voltage at the switch or control board. It is also important to check the battery voltage, as low voltage can cause intermittent and random problems. Most 12V devices will not function below about 10.5V.
So, when troubleshooting 12V problems, first check the voltage at the batteries and/or converter. If the coach is plugged in and the converter is functioning, the battery voltage should be over 13V. Next, locate and check the fuse. Probe the failed device to see if it is getting voltage. Finally, probe for voltage at other obvious locations along the line, such as switch and control board. If you can’t identify the problem, seek out the assistance of an RV service center. If you lose all your 12V circuits, first check the battery voltage. If you are plugged in to shore power and you lose your battery voltage, check your converter fuses and breaker. The converter will have a breaker on the output and fuses on the input. If the converter is separate from the power distribution panel, it will likely be installed behind a coach wall (likely behind the breaker panel), and will have to be accessed to check the fuses. If the breaker and fuses are okay, your converter may need to be replaced.
Next week I will finish this series with a continuation of electrical troubleshooting
About the Author:
Steve Froese, an avid RV owner, traveler, and Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.
