Open neutral somewhere in circuit...what to do?

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  #1  
Old 08-04-13, 06:12 PM
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Open neutral somewhere in circuit...what to do?

a little background...
the house was built in the 1920s...so pretty much plaster on wood lath. all the wiring is BX (aka armored cable).

the breaker box is relatively new and the open neutral issue has been there before and after the box was replaced.

so how do i go about looking for this break?

for some reason if i turn the load off the circuit for a while i'm able to turn a light on...but if i put any load on it...it's out or if the light is on for any length of time it's out...i think...never got around to test that but the wife said it goes out.

i checked all the outlets and they were all replaced and power was fine prior to this outage. no stub on the outlet and terminals...they are all looped around the screws. i basically pulled every outlet and checked and rechecked. i even changed out all the wire nuts and nothing.

oh and just to note only part of the circuit is down. the other ones work perfectly fine.

what else can i do here?

thanks for reading.
 
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  #2  
Old 08-04-13, 07:39 PM
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Your wiring is almost 90 years old, it's time to start rewiring the entire house for modern appliances and loads. It is well beyond the end of it's useful life.
 
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Old 08-04-13, 08:03 PM
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oh and just to note only part of the circuit is down
How do you know it's the neutral ? An intermittent hot wire will cause the same problem.

You need to identify the circuit. Turn the breaker off that supplies that circuit. Find and write down everything that is on that circuit. Now look at your list and you'll know which devices to check. You will need to check working locations on that circuit as well as the ones that go out.

I've never known wiring to go bad with age. The copper wiring will last indefinitely. It's the insulation that defines it's usefullness. When the insulation's integrity is comprimised.....then it's time for new wire.
 
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Old 08-04-13, 08:53 PM
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volt meter reads about 60ish volts when hot and ground is connected.
when checking the neutral it's a lot lower...i think like 10 or somewhere around there.

is there a way to put in new wire without destroying the walls? this is a 2nd floor bedroom...finished attic.
 
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Old 08-04-13, 09:17 PM
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Are you using a digital multimeter? If so plug in a lamp and take the readings with the lamp turned on. Are you using a known good ground? If you have a newer grounded receptacle with a known good ground use an extension cord from there as your ground.

Use that same extension cord as a reference to check hot and neutral at each receptacle. Wide slot is neutral; narrow slot hot. Tests must be made with cable disconnected starting with the box closes to the the breaker panel. While the circuit may not really run in a strictly linear route it is best guess.
 
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Old 08-04-13, 10:05 PM
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yes it's a fluke digital multi meter.

should i still take a reading when the lamp doesn't turn on or are you referring to plugging the lamp into the other outlets that work in the circuit?

ok i'll give it a try.
thanks!
 
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Old 08-04-13, 10:22 PM
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The lamp should be plugged into the receptacle you are testing. A digital meter sometimes gives an inaccurate reading do to high impedance so we usually recommend an analog meter to give a truer reading. The lamp adds the load a digital meter lacks. With a digital meter any reading as low as you are getting is probably not real. Just a ghost reading from induced voltage.
 
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Old 08-04-13, 10:27 PM
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I once had a similar problem years ago before I started working on the house. It was a floating neutral because the neutral connection was bad on the telephone pole whenever it got windy outside, and probably the house had a bad connection to the ground rod as well.

In your case I would start by making an electrical map of all the house circuits. It takes several days of experimenting turning things on and off and crawling around the attic peeking inside junction boxes with a voltage detector, but it helps troubleshoot these things enormously.
 
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Old 08-05-13, 08:34 AM
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peeking inside junction boxes with a voltage detector
If by voltage detector you mean non contact tester they are nice toys with a couple of legitimate uses but useless for any kind of serious troubleshooting. An $8-$15 multimeter is best choice. Digital meters are okay but cheaper ones can be influenced by induced voltage.
 
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Old 08-05-13, 08:44 AM
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A non contact volt tester is very useful to trace circuits when the house is wired with NM cables. Someone can turn a suspected breaker on and off repeatedly while you hold the tester to the cable.

For checking voltages, I got a lot of misleading results with a digital volt meter because of induced currents. I quickly learned the only thing I could get reliable results with is a Wiggy, one of those volt meters that ignore the stray currents.
 
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Old 08-05-13, 08:46 AM
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You should write down the test results for all receptacles. This way you can help narrow down on where in the daisy chain of each circuit the problem might be.

Most likely a loose connection at the first bad receptacle or at the last good receptacle.
 

Last edited by Nashkat1; 08-05-13 at 10:50 AM. Reason: Typo
  #12  
Old 08-05-13, 07:47 PM
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ok so i'm getting close...
i found the last good circuit/outlet and the first bad one. i think i lost a few pounds running up and down the stairs turning breaker on and off.

i assume there's something that's disconnected between the last good and last dead box?

so what's my next move?

thank you all for your input you have given me so far.
 
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Old 08-05-13, 09:11 PM
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Disconnect the cable between the working and nonworking receptacle on both ends. Using a multimeter set to resistance and a long enough wire to run between the two ends check the continuity on the black wire and the continuity on the white wire.
 
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