Question: My battery is fully charged and the inside lights work when I plug into AC power, but not off straight battery power. Fuses look fine.
Answer: Lets start with the most obvious problems. First, do you have a battery disconnect switch? Is it activated to shut off power from the battery? If it is, then turn it off and you should have your lighting back.
Next, is the lack of 12 volt power just at the lights or are all 12 volt appliances not operating (i.e., fans etc.)?
The next few steps require some knowledge and comfort working on a live 12 volt circuit. If you do not have experience or are uncomfortable then take your rig to a qualified repair facility. If you attempt to go further and you make a mistake then you could be letting yourself in for a very costly repair and or injury to yourself or others. Please do not proceed unless you have experience with trouble shooting 12 volt systems and have physically disconnected from shore power.
Are you battery connections clean and tight? If not, then clean the connections and tighten the cables. Did that fix the problem?
The next step is to trace the 12 volt wiring from the battery to the converter:
Are there broken wires (positive or ground) from the battery that would affect all lights? This step will require that you trace the positive and ground leads from the battery to the fuse or fuses. Your best option is to use a volt meter and test until you do not get a reading.
The power leads will eventually go back to your converter and the DC breaker box. Have you ever seen the inside of a converter? Can you identify the battery connections. If not, take your rig to a repair facility. If you have seen the inside of a converter and are comfortable working on a live 12 volt circuit then proceed to see if you have 12 volt power at the converter.
The converter is the common point from where 12 volt battery or 120 volt power is distributed to your lights and appliances. If you have 12 volt power at the DC breaker box connections and the converter, then the converter is faulty. There are several components in the converter that can go bad.
So here is a link to a very experienced RV’er that has taken the time to download diagrams, trouble shooting and repair information on his particular brand of converter and another brand. Since different converters generally do the same thing, most of what is in the link will suffice for other brands as well. Here is the link.
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