The 12 Volt Electrical System On My RV Only Works When I Am Plugged In

by Lori
(San Diego)

The 12 volt on my trailer is not working but when I plug into 110 everything works what am I missing? Tested inverter and electric getting to it.

ANSWER: Greetings Lori thanks for submitting your question on our Ask An RV Question Page.

My gut instinct from what you have told me is that it is one of two problems. The first one could be that your house batteries have gone bad and are no longer accepting a charge or your RV's Converter is no longer charging your house batteries.

First I need to clarify something for you and other RVers. In your description you stated that you had checked your RV's Inverter and that it was getting power. I think you meant to say was that you had checked the RV's Converter. There is a difference between the two. Please see the definitions below.

Power Inverter: A Power Inverter wires into your RV's 12 volt DC electrical system or directly to your house batteries and changes the 12 volt DC current into 120 Volt AC current. You plug in your 120 Volt Appliances directly into the plugs on the inverter. Inverters are great for running TVs, Laptops, etc when you are not hooked up to electric or running a generator. Inverters are not good for running the RVs Air Conditioners or Microwave Ovens as they will drain your RV's House Batteries.

RV Power Converter: An RV Converter basically supplies 12 Volt DC power to your RV when it is plugged in or the generator is running. So when the RV is plugged in the Converter takes the place of the RV's house batteries and while the RV is plugged in most Converters also charge the RV's House batteries.

We need to determine if it is the house batteries or Converter causing your problem. We know that the part of the Converter that supplies 12 volt DC power is working, but we do not know for sure if the battery charging function is working.

Please follow the troubleshooting steps I outlined in the answer I gave to this question: Our RV Interior Lights Only Work When We Are Plugged In Or Generator Is Running Hopefully this will help you find the problem with your trailer's electrical system.

There is also a book I recommend to any RVer that would like to learn more about how their RV's electrical system works as well as how to troubleshoot RV electrical problems it is RV Electrical Systems: A Basic Guide to Troubleshooting, Repairing and Improvement By Bill and Jan Moeller.

I hope that all of this information has been helpful to you.

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Happy RVing

RVing Al