Interior Floor Lights

[KYAvion]

The bottom wire in the pic blows the fuse. What else is fed by that same fuse? So you’re saying that bottom wire feeds the ceiling light or the switch? And in the path to whatever it feeds is a short that’s blowing the fuse? Any chance the ceiling light is the problem? Maybe remove it to rule it out?

[silverloaf]

KY-

All my testing was performed without the ceiling light.

Below are some pics that might clarify the issue. The first pic shows the 4-gang switch on the wall. All lighting sources from this gang of switches get their power through the top 12V-20A fuse on the panel. The left switch controls the ceiling light.

The second pic shows the wiring at the ceiling light. The wire with the wire nuts run to the wall switch. The wires that are folded and taped is the set that disappears though the ceiling. When the 2 sets of wires were connected together, it blew the fuse. When disconnected and with a new fuse, I got un-interrupted power.

The last pic is a repeat of the one posted earlier. For this test, I used a 12v power supply under the fridge (barely seen in the pic). This circuit is controlled though the 4th 20A fuse in the panel. I connected this wire set to the bottom one in the pic. It blew the fuse.

After disconnecting the wires and replacing the fuse, I connected the power supply to the floor light wires. No blown fuse. My conclusion is the looped wires in pic 2 and the bottom wires in pic 3 are one and the same.

Here's how I think this ceiling light circuit is supposed to work: The left wall switch provides power to the ceiling and floor lights. The floor lights come on every time the switch is flipped. The fluorescent ceiling light has a rocker switch. It can be turned on or off while power is still flowing to the floor lights.

This why I conclude there is a short in the wire from the ceiling light to the floor lights. During the restoration process, I have found some dubious installation of wires. Some have a rubber grommet around a hole in the metal; some do not. I've also found bare wires protruding from a wire nut in contact with metal. Maybe somebody spiked the wire with a screw. Who knows?

No...I can't take a short in a wire and just lengthen it

[KYAvion]

KY-


The second pic shows the wiring at the ceiling light. The wire with the wire nuts run to the wall switch. The wires that are folded and taped is the set that disappears though the ceiling. When the 2 sets of wires were connected together, it blew the fuse. When disconnected and with a new fuse, I got un-interrupted power.

You got uninterrupted power to both sets of wires? I assume the answer to this is NO. At least it should be if I’m understanding things correctly.

[KYAvion]

“After disconnecting the wires and replacing the fuse, I connected the power supply to the floor light wires. No blown fuse. My conclusion is the looped wires in pic 2 and the bottom wires in pic 3 are one and the same.”

You’re probably right. How about testing them for continuity?

[KYAvion]

“Here's how I think this ceiling light circuit is supposed to work: The left wall switch provides power to the ceiling and floor lights. The floor lights come on every time the switch is flipped. The fluorescent ceiling light has a rocker switch. It can be turned on or off while power is still flowing to the floor lights.”

This is how my 30R is wired, with the exception being that I don’t have the floor lights.

[KYAvion]

So if you supply 12v to either end (at the fridge vs at the ceiling) of the wire that you suspect to have a short, it will blow the fuse? Right? I assume Blue is the 12v? Try reversing it. Supply 12v to the white and use the blue as your common. Work fine? I’d think so since the shorted wire is now serving as common and the short is going to ground. Measure the voltage of your skin though to make sure it’s not carrying anything.

Thinking out loud here. Another option to get things working... could you use whichever SINGLE wire isn’t shorted (I’d assume it’s the common, or white, since I don’t think a short on it would blow the fuse unless it’s contacting your hot somewhere???) as your 12v supply (tape it RED to label appropriately as 12v), and then run your floor light’s common to the skin? In this case, you’d just fold back both ends of your original 12v wire (blue wire) and tape it since it would be unused and now eliminated from the circuit.

[Salty]

What would you do?

1. Is the hot wire that is blowing the fuse an add on or is it original? The reason I as is that original wire is run under the foam insulation and an add on wire is run outside of that. An add on wire I would use as a pull and route a new wire. Failing that, I agree w/KYavion and turn the ground/negative wire from the ceiling light into the hot and either use ground/negative from the fridge area.

2.My LP gas level switch on my command center is useless. Replace the switch there with DPST switch , run power up from the fridge area and then back down to the device wires

[silverloaf]

In response to your questions:

1. The wire is original. It is the same color (blue/white with brown jacket) and gauge (14-2 stranded) as the other12v wires in the trailer. To have made it an add-on wire would require dropping the ceiling and removing the fridge to run it across the ceiling and down the wall. Sounds like work.

2. Any separate power supply from the panel to the blue wire in the jacket blows a fuse. It doesn't matter whether it's connected at the ceiling light or back-fed from the fridge. I have 4 blown fuses from 2 different circuits to prove it.

3.Flip-flopping the wires from the hot to neutral and visa versa is a great idea! Wouldn't that mean the metal in the trailer becomes both neutral and ground feed back to the panel? It's like using the cold water pipe in a house as a common neutral connection rather than running them directly to the panel.

4. If all else fails, I'll try snaking new wires somewhere behind the stairs. The wires for the exterior step lights run through holes in the floor diectly below the 4-gang switch and fridge. Since all my interior lighting will be LED, maybe I can use 16 gauge instead.

Thanks for all the input.

[KYAvion]

“Flip-flopping the wires from the hot to neutral and visa versa is a great idea! Wouldn't that mean the metal in the trailer becomes both neutral and ground feed back to the panel? It's like using the cold water pipe in a house as a common neutral connection rather than running them directly to the panel.”

Well, sort of. I’m not an electrician, so I may be off on some terminology here, but since it’s DC I think technically it’s just a “common” wire, and not a neutral as would be the case in an AC circuit. And since it’s DC, you don’t have a separate ground like you do in an AC circuit. So with DC that common wire is just a return path for the 12v.

So yes, in an OLD house THE GROUND (NOT THE NEUTRAL) might be connected to a water pipe. At any rate, in your trailer you’d never connect a 110v neutral to the trailer skin, because the 110v neutral and ground separately go back to the shore power neutral and ground, where they lead back to the main service panel where ground and neutral are bonded and literally go to copper rods in ground. Plus you wouldn’t want 110v going from neutral to the skin. That’s AC, or 110v. We are talking about your trailer light, which in this case is DC.

So the return path for your 12v lights in your trailer is the common wire, which is eventually bonded to the skin of the trailer. In my former 79 Airstream I had lots of 12v hots, but no common wires. That is, everything was just bonded to the skin, which is what your white common wires are doing anyway.

Again, I’m not an electrician so hopefully someone with more expertise in this area can explain it better. But that’s the general idea of things...bonding the return path to the skin is ok since we’re dealing with 12v DC, but that’s NEVER ok with 110v AC.

[KYAvion]

Something worth mentioning is that it’s a good idea to carry a no contact voltage tester for testing your trailer skin after plugging in at a campground. Do this before touching the trailer, steps, anything. While you’d use a low voltage tester for this, the issue lies with AC and thus would really belong in the 110v AC section. However, this discussion has made me think of it, so I thought I’d bring it up. Sometime google Reverse Polarity Bootleg Ground.