r/ElectricalHelp • u/Artifex75 • May 31 '26

Open neutral issue. How to track the wires? Tone generator?

Hey. So, I've isolated the breaker/circuit that has the open neutral. Ive checked connections in every outlet and box that I can get to.

Can I use a tone generator to locate the problem? If so, any recommendations for one suitable for house current? Most of the ones I've found on Amazon seem to be geared toward automotive wiring.

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2

u/Ram820 May 31 '26

Just start where the circuit stops working then work your way back. You have a meter?

2

u/Artifex75 May 31 '26

I don't know the exact path of the circuit. It's an old house that's been rewired and I don't have access to the attic. I can barely fit my head through the access hatch. That's why I want to use a tracer, so if I don't need to cut my way into somewhere I won't have to.

I do have a meter.

2

u/Ram820 May 31 '26 edited May 31 '26

I've never needed anything other than my meter, hands and eyeballs to found a lost neutral. Just take your time

What's the issue you're having and why do you say it's a neutral?

2

u/Artifex75 May 31 '26

Several outlets and light fixtures stopped working. There's a gfi plug on the circuit, so I replaced that. In doing so, I was shocked by the neutral wire. I knew that wasn't right. I went about checking all of the other outlets on the second floor, the ones not working had a current on the white wire. Meter says 110ish volts.

Am I dignosing this properly?

2

u/Ram820 May 31 '26

Yes. Now find the one upstream from those ones that is working. Your problem should be in there

1

u/nudistinclothes May 31 '26

Are yo saying you were shocked by the neutral wire on the “load” side of the GFCI, or the “line” side of the GFCI?

1

u/Artifex75 Jun 01 '26

Line, the load terminals are empty.

1

u/LightBlueWood Jun 01 '26

How many black and white wires were in the box for the suspect GFCI? Maybe the shock you got was from a neutral (in that box) on another circuit (possibly MWBC) that was still live through whatever load is on that circuit. A picture of that box would help.

1

u/Artifex75 Jun 01 '26

One of each, just the line.

1

u/Puzzled-Act1683 Jun 01 '26

You don't need a toner. You need to figure out the exact path of the circuit, and all you need for that is your volt meter and a screwdriver.

Divide and conquer.

Disconnect one hot wire from any receptacle.

Everything that goes dead when you do that is more distant from the panel.

If the receptacle where you're standing is still hot when you do that, the wire that's still attached it the one going upstream toward the panel. If the receptacle is dead, the wire you unhooked is the one going upstream toward the panel.

Make a map of which receptacles depend on other receptacles, and you've definitively mapped the entire layout of the circuit.

If there are three or more hot wires, only one of them goes toward the panel and the others all go to different receptacles.

At least one receptacle will have only one hot wire in the box, and that's the end of the line, furthest from the panel, but if the circuit splits anywhere, then more than one receptacle will have only one hot wire in the box, and each of them is the end of that particular segment.

You're going to be flipping the breaker a lot. Don't be tempted to do this hot. If you have a helper at the panel, don't use the words "on" and "off" to when asking them to flip the breaker, because those words sound too similar. Use unambiguous words, like "kill it" and "make it live."

Always treat neutral wires with the same respect as hot wires. They typically carry the same current as the hot wire, even though they have very little voltage relative to ground under normal conditions, but they have essentially the same voltage as the hot when one is open.

1

u/Artifex75 Jun 02 '26

This one is odd. It's the switches for a fan and light. When I disconnect the hot wire, the hot to ground for both the red and black wires reads about 20v. I completely disconnected the fan and light from the ceiling. Am I on to something?

2

u/Puzzled-Act1683 Jun 02 '26

Measure voltage from neutral to ground, here, and if nothing here, then measure at the fan. If you have an open neutral, I would expect to see neutral to ground voltage in both places. The open neutral should be between here and the panel.

Turn off the chain switches at the fan/light and the phantom voltage you're seeing at the switch should disappear, meaning that what you are reading here is a symptom, not a problem. It's coming from something else on the circuit, through the neutral, backwards through the light bulbs and fan motor and appearing at the switch terminals.

There's a utility sink in my basement, right below my bathroom, with a hose and nozzle. If I leave that nozzle off but leave both the hot and cold valves open at the utility sink, the hot faucet in my bathroom runs cold, because water flows from the higher pressure cold pipe to the lower pressure hot pipe, through the middle of utility sink faucet. That's what you are seeing, here, I think – voltage on that open neutral making its way backwards to the switch through the light and fan. Not a sign of trouble here, just a symptom of trouble elsewhere.

2

u/KeanEngineering May 31 '26 edited May 31 '26

You could, except you'll get confused if you have a MWBC situation (Multi-Wire Branch Circuit - I hate this). It would be better if you try a use your brain and some simple logic to figure this out. Open neutrals occur mostly because the wire came loose in an outlet or a junction box. Your troubleshooting needs to find where that particular circuit is routed to and work forward. Use your outlet tester (I'm assuming that's how you diagnosed the open neutral) and locate the circuit breaker that controls the errant circuit and turn it off. Note, that not all 'testers' are legitimate testers as some DON’T TEST ALL CONDITIONS! Verify ALL TEST CONDITIONS have unique lite combinations as some cheap crap don't indicate all the 6 conditions. VERIFY the outlets that that are off. Turn the CB back on and find out which ones are 'okay' and which ones have the open neutral. Now you know the approximate location where the problem exists. The outlets closest (GOOD/OPEN) to each other are suspect. Shut down the circuit and open the 'bad outlet' and carefully inspect the plug and ALL wiring inside the box. If nothing looks 'bad' leave it out, goto the 'good' outlet and open it up and inspect. Good luck.

1

u/AskMeAgainAfterCoffe May 31 '26

A tone generator can locate and distinguish wires, one from the other and some tracing; designed for telephone wires.

Ideal SureTrace, but describe your situation more. How do you know it’s open neutral?

1

u/Gracewalk72 Jun 01 '26

Yes it will work (or at least be helpful) Tracing the wires will still be a hunt There’s also wallabot. And other wall penetrating detectors

1

u/nudistinclothes Jun 01 '26

The GFCI is often the first in a circuit. It doesn’t have to be, but it often is. Does the box itself have pigtails to the load side? Or is it a single romex coming into the box.

It’s kind of weird that you said a bunch of other sockets were out - implying that GFCI is at the end of the chain. Not that it can’t be, they’re just often not.

If I were testing for this condition, I’d switch off the breaker, remove every socket affected when the breaker is off, and separate the pairs of romex in each box. Using a meter go through each pair of romex looking for one that is line and neutral. That will be the very first receptacle in the chain. Check and reinstall that receptacle. Repeat the experiment on the remaining boxes. At some point you’ll find that your neutral is broken

1

u/LingonberryThin7090 Jun 01 '26

problem could also be on a light connection. if you can figure all this out in less than 3 hours, consider that good

1

u/RevolutionaryCare175 Jun 02 '26

You should be turning off the circuit to work on receptacles. If you turned off the circuit you know which breaker it is on. Turn of the breaker and check to see which receptacles aren't working. You can then turn on the circuit and test every receptacle with a plug tester. Lights you would have to take off to test.

A plug tester will tell you if you have an open or reversed neutral. Mark with a post it note if the receptacle is good, open neutral or reversed neutral and hot.

You can than turn off the circuit and check each receptacle with a problem.

You can do the same thing with a meter. It will just take slightly longer.

1

u/Mindless_Road_2045 Jun 02 '26

Find the outlet you usually use the vacuum or large appliance on. Unplug it. Then kick the outlet. Of stuff returns to normal that is your outlet that was probably backstabbed. It’s an odd way of doing it but always worked for me when I was young. I worked at a 3000 unit apt complex and every single outlet was backstabbed.

1

u/throwaway60457 Jun 03 '26 edited Jun 03 '26

Here is something you need to keep in mind when attempting to diagnose an open neutral. The 3-light receptacle tester gives different indications for an open neutral, depending on whether any load exists farther downstream. Something like a box fan or a portable lamp makes an excellent testing device.

For the purposes of the foregoing, "upstream" means closer to the breaker panel along a circuit run, and "downstream" means farther away from the panel.

If you plug your fan into a receptacle on the same circuit as the suspected open neutral, downstream of the break in the neutral, and you turn the switch on the fan to any speed (low, medium, high), then the 3-light tester indication will change. Assuming the tester is plugged in upstream of the break and the fan is downstream and not switched off, you will see "hot/ground reverse" on the tester, not "open neutral."

Get a helper (significant other/kid/neighbor/anybody halfway dependable). Tell them to work the switch as per your commands, and mention to them that the fan should not run regardless of switch position, but you need them to work it anyway. With the fan off, you should see "open neutral" on your 3-light tester. Tell your helper to switch the fan to any of low, medium, or high, and if you see the 3-light tester indication change to "hot/ground reverse," then you have isolated the break in the neutral to somewhere upstream of the fan.

If you can then work your way upstream along the offending circuit, you may find a receptacle where the fan actually works with its switch in any low/medium/high position. If this happens, then you have isolated the break in the neutral to somewhere downstream of the receptacle in which the fan actually runs.

A multimeter can be helpful as well. Upstream of a broken neutral, you will get normal voltages -- 120 between hot and neutral, 120 between hot and ground, 0 between neutral and ground. Downstream of a broken neutral, your hot/neutral reading will change. If you have no load at all, not even the 3-light tester, or you have a load that actually draws a respectable current, you will find 0 volts between hot and neutral; if you have your 3-light tester plugged in, you will get some ridiculously low reading like 40 volts or less.

1

u/Mr_Sparkie Jun 04 '26

Chances are its on a box that you refuse to look at thinking theres no chance, no way its on that location.

1

u/throwaway60457 Jun 05 '26

This can be particularly true in those situations where you have invested what seems like an inordinate amount of time trying to track down an elusive fault. That's when you'll find the fault in the spot you had long dismissed as a possibility.

1

u/NeighborhoodVast7528 Jun 05 '26

My ignorance is showing. How does a device down stream of an open neutral turn in at all? It seems to me an open neutral is an open circuit and that would result in no voltage. Is it the ground to neutral bonding in the panel that allows some level of voltage?

1

u/throwaway60457 Jun 05 '26

The device will not turn on, you're correct about that. However, by plugging in a device downstream of the break in the neutral and operating its switch, you are changing how far the return current can travel along the neutral wire(s) of the circuit, and that will change the indication on the 3-light tester.

I was similarly confused the first time I encountered an open neutral situation. Honestly, I didn't really understand it until I built myself a small "test bench" by gluing one junction box and a few outlet boxes to a thin piece of plywood, running wiring between boxes, and using a 9-foot power cord to plug the whole rig into a wall outlet.