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#1
Old 12-24-2006, 11:18 AM
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How can I trace a break in electrical wiring within walls?

A couple of external lighting sockets died at once. The bulbs test fine and the other lights on the circuit are on. Removing the sockets, I found no live wires in their junction boxes.
I'm presume the break is somewhere in the walls between those lights and the circuit breakers, but I don't know which socket is closest to it, nor whether the wires travel along the top bottom or middle of the walls.

All the conduits are buried in the stucco and are plastic- not sure if that helps or hinders.

My non-contact voltage probe will only trace live lines. Is there a way to trace wiring without current? Is there a way to apply a small current to the dead sockets so I could at least trace the wiring path between them.

Before I call an electrician I'd like to know what he would be able to do sort this out.
Thanks
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#2
Old 12-24-2006, 11:46 AM
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Quote:
Originally Posted by According to Pliny
My non-contact voltage probe will only trace live lines. Is there a way to trace wiring without current?
Non-contact probes will detect conductors which have no current through them, as long as they are energized. This is why they are excellent for determining which bulb in a series string of Christmas lights is bad.

However, there are other possibilities besides a physical break in the wiring (which would be unusual in the absence of rodent infestation or earthquake--wires in walls don't just break for no reason). Check the switch(es) which control the light, if present. You will need to also check the junction boxes between the circuit breaker/fuse panel and the fixture; these should be readily accessible from either the attic, basement or the crawl space. The NEC requires that all such junctions be accessible, that is, not walled up behind drywall; it's just a matter of finding them. Sometimes junctions are made inside electrical outlet or switch boxes, so check them, too. You're looking for loose or corroded wire nuts or other evidence of a faulty connection.
#3
Old 12-24-2006, 12:19 PM
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The problem is that the junction boxes are stuccoed over (the previous owner thought they were ugly I guess and didn't check the code) so I don't know where they are, except the ones at the fixtures themselves, which I have checked by direct bare wire contact with a multimeter.
The only switch (a sensor) is fine, since the other lights go on and off at night.
#4
Old 12-24-2006, 06:09 PM
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External sockets are commonly protected by GFCIs, at least in newer construction. And to save money, contractors often install 1 GFCI in a part of the house which protects down-stream sockets located someplace else.

At my house a 4-plex outlet in the garage is protected by the GFCI in the upstairs bathroom over the garage. Ask me how long it took to figure THAT one out.

The wire run from GFCI to socket was only about 10 feet straight down, so I understand (now) the logic from the builder's POV. But it was NOT conceptually obvious to me that a kids bathroom GFCI would be controlling a garage outlet. So I didn't look there for a very long time.

An idea to consider; it has the advantage of being easy & nondestrcutive to pursue.
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#5
Old 12-24-2006, 06:34 PM
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Quote:
Originally Posted by LSLGuy
External sockets are commonly protected by GFCIs, at least in newer construction. And to save money, contractors often install 1 GFCI in a part of the house which protects down-stream sockets located someplace else.
This is possible, but unlikely, given the description of the scenario. It's true that a single GFCI can protect up to six downstream fixtures or receptacles (per the NEC), but since only some of the lights are nonfunctional and they are all controlled by a single photocell switch, this seems unlikely to be the cause here.

I did think of something the OP apparently hasn't thought to check, however: it seems likely, nearly certain, that all of the lights are wired together. You should therefor check the connections in the boxes for ALL the lights, to see if any of them seem questionable. I would, in fact, pull off all the wire nuts and be sure the conductors are clean and unbroken. Replace them with fresh wire nuts if any of them seem dirty or corroded.
#6
Old 12-24-2006, 07:40 PM
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I am having a hard time picturing a connection inside a box going bad without some type of outside influence.
I would be very concerned about rats. if the house is wired with romex, rats can and will chew the wires. Needless to say this could lead to a fire.
#7
Old 12-24-2006, 07:50 PM
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Quote:
Originally Posted by According to Pliny
All the conduits are buried in the stucco and are plastic- not sure if that helps or hinders.
It helps - wires don't just go bad and there is at least some protection around the wires, so the open is probably due to a bad connection in a outlet or junction box. If you know how the circuit is laid out in your home then you can probably just follow it box by box towards the panel.

In the rare chance that a wire was broken (perhaps by someone driving a nail into a wall at precisely the wrong place), you can use the old wires to pull replacement wires.
#8
Old 12-24-2006, 07:51 PM
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Quote:
Originally Posted by Rick
I am having a hard time picturing a connection inside a box going bad without some type of outside influence.
These are outside fixtures. I would suspect corrosion first.
#9
Old 12-25-2006, 09:11 AM
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Iíll be watching this thread.

My Mom just had one outlet and a ceiling fixture go bad. All breakers in our case are working.

This just happened about a week ago, and I tried to puzzle it out over the last two days.(Iím visiting for Christmas).

60 year old house. No power to the light switch, or the outlet, or the fixture in the ceiling. The outlet and switch are Ďdead endedí in that nothing else is powered from them. The power for them must be fed from the ceiling fixture, but a multi meter does not pick up any power there either.

The outlet is not switched (as in it is not controlled by a wall switch).

To satisfy my Mom, I replaced both the switch for the ceiling light and the outlet. But of course since there is no power there, it did not make a difference.

I think it must be a bad wire (though I have never seen that before).

My Mom is going to get an electrician next week to come check it out. Iím out of ideas.
#10
Old 12-25-2006, 11:23 AM
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Quote:
Originally Posted by enipla
My Mom is going to get an electrician next week to come check it out. Iím out of ideas.
Again, it's probably a bad connection inside a junction box. If the problem isn't inside the boxes of the dead fixture(s), then it must be further upstream. Breaks in the actual wiring are rare in the absence of the kind of things which have already been mentioned to cause them.
#11
Old 12-25-2006, 01:03 PM
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I guess what I was hoping for was a magic sensor of some kind.

The phone guy had a beeping plug-in machine that put a signal on a dead phone socket, and then his sensor wand would beep as he followed the line up one wall and down the next, into the attic and down to a break.

Of course, that was on interior walls, which I presume is more transparent to such devices.

I suppose I just have to start chipping out stucco to see what goes where.
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#12
Old 12-25-2006, 01:09 PM
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Quote:
Originally Posted by According to Pliny
I suppose I just have to start chipping out stucco to see what goes where.
Why start randomly chipping stucco? The light fixtures should be mounted on a standard 4" junction box which is normally flush with the mounting surface (and hence, not visible). There should either be two screws on opposite sides of the fixture base or a single central screw which mates with a bracket, which in turn is affixed to the junction box with a pair of screws. That's where you want to start.
#13
Old 12-25-2006, 01:10 PM
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Quote:
Originally Posted by Q.E.D.
You should therefor check the connections in the boxes for ALL the lights, to see if any of them seem questionable. I would, in fact, pull off all the wire nuts and be sure the conductors are clean and unbroken.
AHA! I got you're saying. I thought you meant check all the dead sockets, wire by wire, which I did, as post #3 said.

But I forgot to check the lights that still work.
The bad connection is probably where the current leaves a working fixture toward the dead ones.

Will check them as soon as it stops raining.
Thanks!
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#14
Old 12-25-2006, 01:12 PM
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To clarify, since you said your voltage sensor found no energized wires in the boxes with the dead fixtures, then the problem likely lies in one of the boxes for the working lights. You want to check those connections physically before proceeding further. Be sure the power is off, and then pull off each and every wire nut in those boxes and make sure the wire ends are clean and intact before securely reseating the nuts (and replacing them with new ones, if they look questionable).
#15
Old 12-25-2006, 01:14 PM
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Ah, yep. You got it now.
#16
Old 12-25-2006, 01:22 PM
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Q.E.D has pretty well covered the situation here, but I wanted to add for enipla's sake, his mother's problem is most likely of the dead switch and plug. A very common culprit in cases like this is a 'stab-in' connection on another plug or switch that is no longer making contact. Check the other devices in the area to see if that is the source. If this is the case, remove the stabbed-in wires and secure them to the screw terminals. If there are too many connections to have only one wire under each screw, then pigtailling may be necessary.
#17
Old 12-25-2006, 01:23 PM
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Quote:
is most likely of the dead switch and plug
is most likely upstream of the dead switch and plug









#18
Old 12-25-2006, 01:29 PM
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Quote:
Originally Posted by Rhubarb
...I wanted to add for enipla's sake, his mother's problem is most likely of the dead switch and plug. A very common culprit in cases like this is a 'stab-in' connection on another plug or switch that is no longer making contact.
I would agree this was a possibility, except that enipla stated that he replaced both the switch and the outlet. I know that stab-in connections can become unreliable over time which is why good electricians never use them, if they can avoid it, however, a brand new installation ought to work fine, assuming the wire ends are clean. It's still possible, of course, but highly unlikely, IMO.
#19
Old 12-25-2006, 01:30 PM
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Quote:
Originally Posted by Rhubarb
is most likely upstream of the dead switch and plug
Disregard my previous post, then. I fully agree with you, and stated as much myself, in an earlier post.
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