How can I find an open neutral?

Question

My lights and outlets went out in the half bath of my home and also the two recessed lights in my hall just outside the half bath.

I believe there are two feeds, one to the hall lights and one to the half bath light and outlets all on the same circuit. I had a plug tester read an open neutral though it was not positively an open neutral as the first yellow light lit but very dimly.

I checked all the outlets and switches for loose wires, etc., but found nothing.

I pulled all the outlets and switches so I had bare wires everywhere. With a multimeter I checked all the hots by touching the blacks and grounds they all read 120V. But when I check any of the neutrals with the meter - one on hot, one on neutral - they drop to nearly nothing ( like .2volts ) so I assumed the open neutral was the problem.

I went to the breaker box and pulled the neutral from the bar and tested the black coming out of the breaker by touching one probe to the black and then to the bar and I read 120. So I assume the breaker itself is OK.

But when I test it with one probe on the black and the other to the now free neutral, I get nothing. So again open neutral somewhere in the circuit, right? I can't seem to find the open neutral anywhere and it's driving me crazy. :(

Am I missing something? Maybe a junction box somewhere?

Answer 1

It sounds like you have a pretty good handle of the problem. Hidden junction boxes do exist but it could also be a failure along the cable.

If you've 100% ruled out all known junction boxes then you need to narrow down the problematic section of cable and go hunting between with a cable tracer. With each section of wiring (ie: junction box to next junction box), test continuity of the cable. You should eventually find the two points where the fault exists between. Once you have this, use the cable tracer to look for hidden boxes and other fun stuff. A flexible scope might help you look in stud cavities. If that fails you might have to open up the wall to get a better idea of what's the problem.

Also inspect all visible wires for nicks, oxidation or other damage.

There comes a point too where it becomes easier to just run a new wire versus trying to find the exact fault location.

If you do find the issue, it would be worth thinking about if it is likely to occur elsewhere and if so, how you should deal with that (replace all the wiring, redo connections in junction boxes, etc.)

Answer 2

Check both the top and bottom outlets when checking GFI receptacles. One might be serving as a junction box.

I have a 1970s home and one GFI feeds two other outlets, one inside in the master bath and one outside. When a worker started his electric saw outdoors, it blew the circuit and it tested with an open neutral. I had tested all of the inside bathroom outlets and they looked fine. After checking the attic for a junction box I found none so I went back to the bathrooms. Turns out that I tested all the bathroom outlets but I did not check every single outlet (2 per box). The faulty one was the top outlet that fed the outdoor outlet and the bottom one was the only one that I checked and it was okay. The neutral feeding the outdoor outlet had burned at the bathroom outlet and broke the neutral connection.

Answer 3

Where several white/neutral wires are tied together in a wire nut in the back of a J-box, take a moment to pull on each wire to make sure that one did not come loose from the connection. This does happen more often than you'd like. A white/neutral wire can just be laying in the wire nut, and not actually be tight with the others.

Answer 4

As others have mentioned, you need to test continuity of every neutral line from the box to the end of the circuit, and then once you have ruled a bad line out, then you should start checking the outlets if they are all carrying the load of the one ahead of it.

To test continuity of the lines you do not need power, just a voltimeter tool so you can shut off the circuit. Starting at the first outlet, set your voltimeter to a low Resistance setting and test the neutral from the lead to the ground wire. You should get a near zero reading meaning No Resistance. Assuming your breaker box was installed correctly, Ground and Neutral should always have near zero resistance as the Neutral and Ground bars at the breaker box should be connected.

If you happen to get 1 or some noticeably higher number then that effectively means Infinite Resistance or that the Neutral and Ground are in no way continuous. That means that effectively the Neutral wire that you have just tested is open from that junction to the prior receptacle's load ( or to the neutral bar if this is the first outlet you have tested).

Once you have identified where the circuit is open, figure out if it is the line or the outlet loading it at the prior outlet box. To rule out the neutral line, you can temporarily connect from the latter outlet box, the neutral line from the lead to the ground. Now walk back to the prior outlet box and test continuity/resistance from the neutral line you are diagnosing to the ground line in the same wire. Again, near zero resistance means the line is okay, 1 or some much higher number means that the Neutral line is bad.

If after this the Neutral line still seems to be fine, though you have identified the break, try replacing the outlet. It could be that the outlet itself went bad.

Answer 5

If your outlets are wired so that the "load" goes through the outlet, then you might have a continuity problem with an outlet receptacle. You need to check the continuity of all the outlets on the circuit if they aren't wired with pigtails and instead have the line connected to one set of screws and the load connected to the other set.

Answer 6

Start troubleshooting with any recent fixture, switch, or outlet work on that circuit. Then trace the problem circuit from the main box outward removing every junction faceplate and inspecting. Jiggle and twist connections while looking for issues. It may be resolved just by a few turns here and there.

Answer 7

The pro solution is a wire tracer -- a signal generator which transmits into the wire, and a receiver which can follow that signal through the wall to see what else it's connected to and where it unexpectedly stops being connected. Used one to discover where my contractor had accidentally cut partway through a wire they hadn't noticed... after their electrician failed to find it. (Good contractors otherwise, so I forgave them the mistake.)

I borrowed the set I used; they're expensive new but I'm told they show up on eBay fairly regularly.

(I've used one of the circuit-breaker-finder sets as a poor man's version of this, but that isn't as sensitive and would just tell you where the circuit goes, not where it's disconnected.)

Answer 8

In the last two steps of the original problem, the readings taken are correct; i.e., that what they should be: Hot wire on the breaker to the neutral bar = 120v; hot wire on the breaker to the LIFTED neutral wire = 0v. If the voltage from the hot wire to the lifted neutral wire is above 0 volts, there is a ground fault on the lifted neutral wire. The readings taken here show that the neutral connections from the utility to the breaker box are ok; and that the neutral is open somewhere in the branch circuit neutral. To find where the neutral is open, you will have to know how the branch circuit is wired--i.e. daisy chained--then start at the first outlet/switch in line checking line to neutral (Blk. to Wh.) voltages. When you get to the device where this voltage is zero, the open is between this device and the previous one tested.

Answer 9

if you have access to the attic look for junction boxes, check to see if wire nuts are tight. open neutral means somewhere there is a white wire not connected or has a loose connection. even under the house could be additional junction boxes to look for.

Answer 10

i agree about the chewed wire being a likely reason. now some information that is not present but is helpful does this circuit consist of the following. breaker connection. 1 red wire + 1 black wire or only a black wire? panel bus bars. 1 white wire to the neutral bus 1 bare wire to the ground bus. cable exiting the panel is it 2 wires aka white+black+ bare or 3 wires aka red+black+white +bare? if the cable this white wire you lifted contains a red a black and the white wire and a bare wire. put the white wire back were you got it off of before you burn the house down. and also the two hots should not be going to separate breakers they should be connected to a two pole breaker with a handle tie so both are switched at the same time. and turn it off until an electrician has been hired to fix this correctly. nobody here wants any of the members to have this happen to them.

Answer 11

If I understand your troubleshooting procedure, I would think that you should call your utility as it appears the problem might be on the line side of the serve entrance section. You can't go wrong by calling.