Trouble shooting 12v lighting issues

[ngiovas]

I am looking for some help troubleshooting a 12v lighting issue in an older travel trailer.

I have a 33' travel trailer (built in 1988) parked on a remote property that I use to stay in while on the property. I have electric and water hookup on site and things have worked well for the past year, but I ran into some issues this weekend.

Everything seemed to be working fine (12v lighting, 110v outlets, fridge, water heater, etc.), but all 12v lighting suddenly died. All 110v items were still working, but all 12v circuits no longer worked. One note, I did convert all interior lighting to 12v LED RV lights when I bought the trailer a year ago. I checked all of the fuses and everything was good. A short while later, the lights came back on for a short time (less than a minute) and then went out again. They came back on a couple more times and finally came on, but were very dim and there wasn't enough power to trigger the valve on my water heater.

I don't know a lot about trailer wiring, but know the basics on automotive electrical. It appears that the previous owner had it wired so that the 12v battery was wired with a cut-off switch and the lighting was run directly off of the converter. The issues I noted above were the same with the battery on or off. I tested the voltage on the battery and even put it on a charger over night just to be sure, but there was no change to the lighting with the battery on or off.

Since this is affected all circuits, I am not sure if it is a converter issue, or possibly a ground issue? Can anyone suggest any troubleshooting tips to help me isolate the issue? If there is 12V at each fuse, should I assume the converter is fine (I still need to go back up with a meter to confirm this)? Also, I would think the lighting would work off of the battery even if the converter wasn't working (the battery was fully charged). There is a bunch of wiring coming out of the trailer next to the battery that is all bundled together with a large wire nut (both positive and ground it appears). This wiring continues to the battery as well. I don't know if this is how it should be wired or if the previous owner did this. Lastly, is there any easy way to connect to a known good ground to test the ground? If something chewed through the ground on one circuit, would that make all of the circuits have an issue?

I am trying to gather as much information as possible so I can make sure I take all of the proper tools with me the next time I go up. I was even thinking of taking a couple of small 12v batteries with me to try to do some testing to see if that fixes the issue.

Sorry for the long post. I'm just not sure where to start and I don't want to throw money at a new converter if that isn't the issue.

thanks,
Nick

[ngiovas]

I wanted to follow up on my original post. It looks like I was able to resolve the issue, but it ended up being multiple issues in the end.

Since my trailer is a few hours from me I decided to pack up a variety of tools including a meter. I also took a new 12V converter and RV electric panel since I knew I couldn't get one locally once up there. The old one was the original installed in 1988. The first thing I did was test the output on the converter and found that it fluctuated. It would output 12V on startup, but fall to 7.5V after a few minutes. It would then randomly not put out any voltage for a period of time. I swapped the converter and panel and immediately had a consistent 12+ volts coming out of the converter.

I also found that the battery was back-feeding the original panel through one of the circuits and fuses. It wasn't connected to the correct terminals on the 12V board, so this was also corrected when installing the new board.

During the swap, I realized someone had wired multiple lighting circuits together using a wire nut after the fuses to join 3 circuits. I cleaned this up so that each circuit was isolated from the other.


I decided to go ahead and check my battery more closely. While it was putting out over 12V, I discovered it was low on water. I topped it off, but will replace the battery with a new one after the winter (I don't use the trailer over the winter).

Finally, with everything up and running (so I thought 🙂 ) I noticed that one lighting circuit at the back of the trailer would occasionally dim/flicker. Knowing there was 12V coming from the output to the circuit, I suspected a ground issue. I followed the 12V wiring to a cabinet under the sink and found a ground block. After checking all of the screws, I discovered one was very loose - yep, it was the lighting circuit.

I ended by inspecting all visible wiring I could find and confirming all connections were tight and there were no frayed wires. I feel much better after going through this exercise.

Thanks for all of the tips. It ended up being a bit more work than I thought it would be, but I'm happy I was able to resolve the issue.

Nick

[enblethen]

Yes, disconnect the converter and try off batteries. If you have a battery charger put it onto the batteries. You may have bad battery or two. Separate the batteries and charge one at a time. Then test for voltage if you have a meter. Fully charged should be around 12.5 or greater.
More then one lighting circuit, would indicate 12 volt big issue.
Does the water pump work?
Make and model of your converter? Early converters had two outputs. One filtered and one dirty power.

[Grit_dog]

Given your (well described) conditions, I think you're on the right track.
Seems like a new short in either the + or - between the DC (12V) fuse panel and the battery or the ground.
If your battery is charged, then it shouldn't have anything to do with the converter theoretically.
And given the 12V power circuits all went on and off a couple times, blown fuse(s) aren't likely unless there is a main 12V fuse somewhere.

I'd check for 12V at the fuse panel + side and also continuity to a good ground (trailer frame or something). May need to make a long jumper wire to test ground.
Good luck!

[ngiovas]

enblethen wrote:
Does it have a battery?
Have you checked for 120 volts AC to the 12 volt DC converter?
Check for 12 volts DC leaving converter. Could be bad converter or if your lucky blown fuse in 12 Volt DC distribution panel.

Thanks for the suggestions. I will check all of the voltages when I return. I did check the fuses and they were all good. There are 4 12v lighting circuits, so if it was a fuse issue, it would lilely only affect one circuit. Plus, I was getting some power since the lights were dim (and occasionally fully on).

There is a battery that was fully charged, but it didn't seem to change anything if it was on or off.

I wonder if I can disconnect the converter and try to run off of just the battery. If I still have the issue, it may be a ground issue.

[enblethen]

Does it have a battery?
Have you checked for 120 volts AC to the 12 volt DC converter?
Check for 12 volts DC leaving converter. Could be bad converter or if your lucky blown fuse in 12 Volt DC distribution panel.