Why Are The 12 Volt Lights On My RV Going Dim?

by Wayne
(Clermont ,Florida)

Have a new 2009 RV and the 12 volt lights seem to be getting weaker by the day. They work but dim. The battery looks new and has water in it. The posts are clean and tight.

I took the ground loose and could see fire jump when I touched it back on. You think the battery has gone bad already. The test switch in the RV shows the battery to be week when pressed.

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

Since you do not tell me whether you have a Motorhome or a trailer, I am going to have to deal in generalities here. There are two common reasons that the lights in your RV are not receiving sufficient voltage. You either have a bad house battery or the house battery is not receiving a sufficient charge.

Just because the battery test switch in your RV shows the battery as being weak; it does not necessarily mean that your house battery is bad, it could be because the battery is not receiving a proper charge. You need to have the battery tested and the charging system checked out. Since your RV is a 2009, it may still be under warranty, if not you will have to have a Certified RV Technician do this and pay for the work.

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The first step they should take is to fully charge the house battery and test it to make sure it is taking and holding a charge as well as running a load test. If the battery checks out OK, then we know that the problem is that the battery is not receiving a proper charge. This could be due to a wiring issue or problems in the electrical/charging system of your RV.

I am going to assume that you have gone into the electrical compartment of your RV to check for any blown fuses or tripped circuit breakers. I am also going to assume that you checked for any in-line fuses that may be blown.

Depending on the type of RV you have there could be several ways that your RV's house batteries receive a charge.


1. The house battery should be receiving a charge from the RV's converter when your RV is plugged into a 120 volt power source.

2. The house battery should also receive a charge when the RV's generator (if equipped) is running; this current also travels through the converter.

3. The RV could also be receiving a charge from the Motorhome’s alternator or the tow vehicles alternator.

4. If your RV is equipped with a Solar Battery Charging system, it should also receive a charge from this system. By the way if you do not have a Solar Battery Charging System you may want to look into installing one on your RV.

Here are some of the best places to get a good deal on a Solar Battery Charging System. Camping World carries Sunforce RV Solar Charger Kits. eBay has a large selection of Solar Battery Charging Systems and Amazon.com has a good selection of RV Solar Battery Chargers.

Another topic I would like to address is that it sounds like you are only using one 12 volt battery to power your RV's 12 volt system. If you plan to do a lot of boondocking, I would strongly suggest that you convert to a dual house battery system. Please read the answers I gave to the questions below as to why I recommend this.

Are 2 Six Volt Batteries Better Than 1 Twelve Volt Battery To Provide Power To Inside Of RV

How Long Will Our Batteries Last When Boondocking In Our 5th Wheel Trailer?

I hope that this information has been helpful to you.
Do you have any suggestions or comments on this topic? You can add them to this page by clicking on the "Click Here To Post Comments" link located near the bottom of this page.

Happy RVing

RVing Al

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