Electrical question for your guys... (theres a video!)

The video helped but we need to see more. Maybe take some stills a little further back so we can see exactly where the wires terminate? By the opposite wheel well or? Is the switch by the door? Please post a photo of the porch light and bulb.

First of all, by code, AC and DC should never be in the same junction box. I'm guessing that the switch was possibly used to cut the DC power to save battery power? The ceiling light appears to be 12 volt, rather than 110. You said the switch is powered now by 110? (sorry can't check the facts in the video)

There are multiple uses the DC wires could have. A water pump, coming out of a converter, lighting, etc.

Hi guys,

Thanks for your feedback. I've taken some photos and I'll try to get them up soon. In the meantime, here is what I've determined to be fact:

When I place the 110 probe on the rear side of the switch(inside cabinet), it lights up whether the switch is up down or off... the probe does turn off when I am physically holding on to the toggle switch... am I the ground?!

The grey line that runs from the junction box through the ceiling and down the closet, under the camper to the step/porch light is a 12v bulb. The step light is cylindrical and I haven't been able to find a replica online (and I have some pretty nerdy google skills lol) which leads me to believe its unobtanium.

The brown wire from the junction box runs through the ceiling and down in to the closet and currently is connected to nothing.

The switched 12v light seen briefly in the ceiling, also runs down the closet and is spliced in with the Brown line mentioned previously.

I have scoured the trailer, head to toe, nook and cranny... and I cannot see any evidence of other jerry rigged electronics, there is no indication that an inverter or converter once lived anywhere so I just can't figure out how these 12v accessories were powered...

I guess it was as simple as throwing a battery in the closet? If so, what was the purpose of having a switch differentiating 110 and 12v?

I guess the next thing to do would be taking the junction box cover off and take a picture of that?

Thanks for your attention to this and helping me solve this riddle!

Still photos would help us. Videos move and don't allow us to study exact connections, etc.

This sounds like a mess to me and not safe.

The best course would be to remove the box, transformer and switch. After disconnecting all power to the trailer, snip the wires as long as possible and leave them in place. They can be re-purposed as you move along. Wrap the ends of each wire or use an electrical wing nut to prevent accidental shorts when power is reconnected.

Using a multimeter, test the wires coming out of the grey sheathing to see if they are "hot" when the trailer is powered up. The meter should read in the 118 to 125 range when on AC. Whichever wires are hot should be labeled as 110 in. See if you can trace these wires to the source of power. It may be the grey cable or other wires.

Do some more testing to see what still works in the trailer. List working lights, outlets and appliances. Obviously the porch and step light won't be operating. My guess is that the switch may have been for the step but from your description, things are not wired properly.

I enjoy sleuthing out electrical. Please answer a few questions:

Where is the switch located?
Does the grey cable enter another J box somewhere?
I'm guessing the 12 volt wires were connected to a battery in the closet. Any marks at all on the floor?

Your trailer can have a safe 12 volt system added. The solution is to start over and get it right.

*UPDATE*
As I putter around this thing, I found an old golf battery and hooked it up to the black leads at the bottom of the closet.

The black lead follows upwards and splits off to to the 12v ceiling lamp and the switch we've been talking about... well, the 12v lamp works just fine AND when I toggle the switch to 12v, the step light turns on. It would seem to me, that these guys just wanted to be able to turn the step light on using shore power or 12v...?

Fire extinguisher and rubber gloves in hand, I'm going to plug in the trailer and see if this is, in fact, just a vintage 110 converter.

I didn't see the transformer in the first video. That's a doorbell transformer, and somebody definitely homebrewed that setup. Looks like a toggle switch with "ON OFF ON" so they can use either the transformer when plugged in to shore power or a 12v battery if boondocking.

Problems I see is 110v and 12v mixed in same box and no fusing for 12v. Also, not sure if those bell transformers are designed for continuous duty.

Thanks Chriss and Whitney, the riddle of the transformer has been solved. Doorbell transformer... you have to take a moment to appreciate someones cleverness.

Few questions to answer:
The grey line is definitely the same line that leads from the switch/junction box to the step light. I replaced a ceiling panel and with it off, I can confirm it was the only line... the ceiling is the only part where it is concealed as it runs down the closet, through the floor and wraps around the undercarriage frame to the step light.

Both of you are correct in that I do not have a fuse block set up for the 12v systems. I just set up a quick small battery to test so since I have confirmed their functions, I'll be cleaning up the actual wiring and creating a cleaner, easier to access, fuse panel. (I'm currently building my solar off grid setup so this will have to wait)

As far as the wiring, it is pretty janky. The toggle switch shows a rating of 125v stamped in... so as homebrew as this was, seems he/she put in components that won't melt and set fire. I will definitely be separating the 110v and 12v leads in to two separate boxes... 110 in a junction box and I will probably solder and heat shrink the 12v stuff.


I hear you about the continuity bit but I would think that since our doorbells are hardwired 110 it should be ok. 


Really appreciate your input!!