12 Volt System On My RV Does Not Work When Not Plugged Into 120 Volts

by Tom
(Indian Harbour Beach, FL)

Everything on my motorhome electric system works well with generator or hooked up to 120v power. Once disconnected the 12 volt systems do not work.

I found a post similar to mine where it was suggested to look around and will find the answer. I looked around and was not successful finding an answer. Help!

ANSWER: Hi Tom, thanks for submitting your question on our Ask An RV Question Page.

Based on your description it sounds like your House Batteries are not providing power to your 12 volt system when you are unplugged from 120 Volt electric or not running your generator. When you are plugged in or running your generator your RV's Power Converter provides your RV with 12 Volt DC power.

Prior to checking the house batteries on your RV you need to check to see if there are any blown 12 volt fuses or tripped 120 volt circuit breakers in your RV. You also need to determine if your Motorhome is equipped with a Battery Cutoff Switch. If it is you need to check the switch to make sure that it is not activated and cutting off the power coming from your house batteries.

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If all of the above is OK it is time to check out your RVs house batteries. I cannot tell you the exact location of your RVs house batteries as the location differs by RV Manufacturer and Motorhome model you have.

Once you locate the batteries the first thing you should check is to make sure that they are properly full of electrolytes, if they are low on electrolytes you need to top them off with distilled water (never use tap water).


If the electrolytes are full then you need to check that the batteries are properly connected. Check for any loose wiring dirty or damaged connections and repair and clean them as needed.

If after you have done all of the above and you still do not get power from the batteries to your RVs 12 Volt appliances then the problem could be either that the house batteries are bad or your RVs Power Converter is not providing a proper charge to your house batteries. In this case, I would strongly suggest that you take your Motorhome in and have a Certified RV Technician diagnose and repair the problem.

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If you are looking for more information on the house battery systems on your RV you should read the answer I gave to Why Are The 12 Volt Lights On My RV Going Dim?

Hope this helps.

Happy RVing

RVing Al

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