12v 'smoke' missing

[motoman]

.....when I replaced overhead 'livingroom' lite assembly in our fith-wheel camper. Both my digital and anolog meters show 12.7v at wire ends. New lite (dual lite/two position slider switch) tested good on battey from its wire ends. Twisted new lite wires onto existing to make sure all was still good before re-attaching lite to ceiling........no joy.
Have come across some really wierd scenarios locating missing 12v 'smoke', but this one's got me baffled. Even stripped back the existing ceiling wires some more for shiny copper. Still have 12.7v on meter off of wire ends. Lite wires hooked up....nothing.
If any of you 12v electrical gurus out there got any ideas what's interrupting the 'magic'smokes' travels, would like to hear them.
Didn't know a ten-minute fix could turn into a 'project'..

[IanDMacDonald]

Well, as an electrician, I can tell you that the "smoke" you refer to is not a good thing. "Letting out the factory smoke" is an inside joke of electricians, referring to burning something up. So, you're just looking for source voltage at the light. Have you tried the light while the RV is running?

[Gmac]

Better yet

Have you tried the light just hooked up directly to a battery?
I smell a defective product.

[ViperRon]

!
12 volts tells me you have potential there but for any device electrical to work it has to have current flow that is what really supplies the power. Check the voltage with the light hooked up and see if voltage drops. Any bad connection burnt up wire corroded connection could drop the voltage and you would have no current flow. But first check the light across a battery, if it will not work there it's defective. And no huffing that magic smoke

[motoman]

Have you tried the light just hooked up directly to a battery?
I smell a defective product.

Initially my thought. No luck, passed the 'snif' test. Like I previously said, even went as far as dropping down one of the other lites, touching new lite wires to those wire connections.....worked perfectly. The new replacement is also identical to original. I would'nt think the meter lead ends being any more conductive reading voltage than the wires connected to each other. Definitely sumptin' goin' on I'm missin'......for whatever reason those wires aren't 'liking' each other.

Ian, it's a fith-wheel, not self-propelled. Both Interstate batteries are new and all other 12v sources work perfectly, as they should. Trailer is 30A service for the 110 portion and inverter when plugged in.

[IanDMacDonald]

Moto- Sorry, I saw 5th wheel, knew what u meant, then my mind switched back to RV for some reason. Okay, second test would be to wire the light as you did, but pull one bulb at a time and turn them on. Check voltage at empty bulb socket. No juice? Could be bad switch. Juice? Could be wrong bulb. I'm wondering the same thing as Ron, and wondering if there is a current issue on that breaker. That would be odd though, as everything else that necessitates a higher draw probs works just fine.

[motoman]

Moto- Sorry, I saw 5th wheel, knew what u meant, then my mind switched back to RV for some reason. Okay, second test would be to wire the light as you did, but pull one bulb at a time and turn them on. Check voltage at empty bulb socket. No juice? Could be bad switch. Juice? Could be wrong bulb. I'm wondering the same thing as Ron, and wondering if there is a current issue on that breaker. That would be odd though, as everything else that necessitates a higher draw probs works just fine.

Breaker box has three seperate 15A blade-fused light circuits. Pulling fuses with all lights on indicated the section locations(several lites on a circuit) of the three circuits. That was more for curiosity, other than to make sure fuses were good.
What's curious though, is new lite works perfectly, switched in either one or both ON position when hooked to one of my vehicle batteries. Even dropped one of the other lites down in camper to access its wires, touching new lites wires to those connections......worked perfectly. Back over to wires where new replacement goes, volt meter says 12.7v......new lite...nothing when wires connected.

[CaptonZap]

Like Viper Ron suggested.
It will take 4 hands, or two hands and two jumper wires.
Take the jumpers, and hook up the volt meter. 12+ volts? Good.
Leave the meter attached, and hook up the light. Voltage go down? Bad
Start tracing those wires back to the panel, and odds are that you will find a wire nut or some such that is not connecting the wire junction together with a clean connection.
If that isn't the answer, you got some BAD juju, and you better lay in a good stock of candles.

CZ

[Schming]

The following may or mayn't help but you may want to check your chassis ground located near your panel/converter box. It should go through the floor and connect to the frame of the trailer.

Also are you plugged into "House" current ?

If so at the battery leads ( battery not connected) you should see 13.6vdc and with a fully charged battery connected ( no load ) the converter should float at 13.2 vdc. With a load (battery connected and lights, furnace etc. on) the converter should show 14.4vdc bulk charge.

If your using just the battery and no house current, through the converter, then my bet is on the chassis ground as I just went through a similar scenario . . . or mice love to chew wires

HTH

[DiverRay]

Also, try to find out how the lights are wired. Does the switch control just the one light, or are there two lights on the same switch? IF two lights, go back to the "working light", and look at the connections from that light on down to the next, not working light. My guess, most of the copper strands in the crimp have let go, and you can show the voltage, but don't have the copper left to run the current.
If the wires are aluminum, as they could be for weight, same thing, but use PLENTY of "NO-OX" on the wires before you re-crimp a connector.
Good Luck!

[BA80]

Check your ground Brant.

[motoman]

Also, try to find out how the lights are wired. Does the switch control just the one light, or are there two lights on the same switch? IF two lights, go back to the "working light", and look at the connections from that light on down to the next, not working light. My guess, most of the copper strands in the crimp have let go, and you can show the voltage, but don't have the copper left to run the current.
If the wires are aluminum, as they could be for weight, same thing, but use PLENTY of "NO-OX" on the wires before you re-crimp a connector.
Good Luck!

Me thinks you're onto it! Lites each have their own slider, two position switch to turn on either one or both lites of each assembly. There IS more than one dual-lite on each of the three lite circuits. With that being said, issue is definitely pointing to those two particular wires that feed that particular lite.
As ViperRon and you have stated, wires seem to not be carrying the current under load when lite is switched on. Also noticed ground wire coming out of ceiling that attaches to lite had a bit of dark discoloration on a few of the wires, so stripped it back a ways farther. Still had a couple darkened wires in spots, but still checked okay with meter. Using my anolog instead of the digital meter, my next 'attack' later this afternoon will be as you and ViperRon has suggested. Look for volt drop or dissapearance of volts when lite is switched on(which I have suspicion will likely happen). Hopefully, the 8in. of ground wire sticking out of ceiling will be enough stripping it back to find ALL shiny copper. May have to source out a can of -De-Oxit locally, if you think that would improve that wires conductivity when attached to another, before cutting it back possibly more than needed...what say you?
Problem being, all wiring being behind ceiling and wall panels, and just pokes out wherever 12v lite locations are makes it not feasible for any wire replacement.

[DiverRay]

Unless you drilled through some wires, problem should be at one end or the other. As I said, check the connection ends, and check CLOSE if they used aluminum wire! Scrape the "black" off the ground, and see if it's copper or silver colored. Depending on the age of the rig, it could have copper plated aluminum for wire. If so, you NEED to use no-ox on ALL the connections.

[motoman]

Unless you drilled through some wires, problem should be at one end or the other. As I said, check the connection ends, and check CLOSE if they used aluminum wire! Scrape the "black" off the ground, and see if it's copper or silver colored. Depending on the age of the rig, it could have copper plated aluminum for wire. If so, you NEED to use no-ox on ALL the connections.

Dropped new lite down to expose wires. Volt meter showed 12.7v at connections. Held meter leads to wire connections at lite and switched on lite......that 12.7v immediately went to 1.5v!
Only De-oxit cleaner product I found locally was at a commercial electrical outfit(CED). It's in a squeeze bottle, but apparently it eats the black off the copper wire strands, same as the spray product. Didn't purchase as of yet.....gonna do some further inspection of that white ground wire coming out of ceiling. Got about 6-7in. left out of ceiling, so maybe going back up wire a few inches and making a razer slice in insulation will find shiny copper, seeing if good contact can be made lighting up the lite? Beyond that, behind ceiling and walls there is no accessing wires.
Wiring IS all copper, even the 110v portion of electrical service visible at fuse panel.

[DiverRay]

Get a roll of wire and tie it down to ground on one end. Use the VOM and check between it and the white ground wire for resistance. Should be no more than 5 Ohms, 10 at the outside if your roll is 50'. Wiggle the suspect wire while you check, and see if the resistance changes.
You MAY have a "bad" ground wire, and may need to see if you can find a way to run a "new" wire. Sometimes a fishtape will allow you to push up through the wall so you can pull a wire on back.