Two days ago, an outlet that had a computer monitor plugged into it went awry. The monitor shut off out of no where. I turned it back on and it powered on for a few seconds before shutting off again. It wouldn’t turn back on at this point. Then, a light switch that shares an adjacent wall, and another outlet along the wall stopped working as well. (The light acted the same way in that it turned on for a moment and then it went off, not able to turn on again.)
I figure they are all on the same circuit. This is in a house built in 1957. These outlets are not grounded and not connected to a gfi and the location is such that there is not a gfi anywhere in the circuit. I measured the voltage at the first outlet by pulling out the outlet and measuring both sets of hot/neutral wires at the rear going into the outlet. Both sets reading around 10V (AC rms). Other working outlets measuring at the expected 120 V. The voltage at the wires for the light switch and the other outlet also reading really low, around 10V. All other nearby outlets measure 120V.
I was expecting to find one set of wires at the rear of an outlet to read at 120V and the other set (associated with the same outlet) , something else = lower implying that the outlet should be replaced. Where else in the circuit would there be a problem leading to this low voltage? Other other help appreciated.
According to my A-Construction Union Electrician son, you’ve lost your neutral. If it’s all of one circuit then it’s in the main box. If it’s the end of a run it is in the last receptical box with full voltage. It will a bad connection, probably corroded. It will not be a broken wire.
Neutral, white wire is what is not connecting. If your outlet has only 1 black and 1 white going to it, it probably isn’t that spot if it’s effecting more than 1 location. If there are 2 black wires and 2 white wires at the outlet, it is most likely feeding the light which is also causing you a problem.
Yeah, this was my thinking as well. I guess I need to go to the next outlet (well, my guess as to the next outlet upstream in the circuit) that is the adjacent room and pull that and measure both sets of hot/neutral. That one has a lot plugged into it, not sure that really matters. Those items are working properly.
Just to clarify: I should see 120 V for one pair going into the outlet, but some other number at the same outlet, but for the other set of hot/neutral.
That 10V sounds like it’s not real voltage but “ghost” voltage - an induced emf on the hot wire.
How was that receptacle wired: was it a single pair of wires coming in? Was it 2 pair and each pair went to a set of screw terminals on the receptacle? Were there multiple wires nutted together with pigtails coming to the receptacles?
I’d say you have something open/broken/disconnected on your hot side. Can walk you through how to troubleshoot it.
Just to clarify: I should see 120 V for one pair going into the outlet, but some other number at the same outlet, but for the other set of hot/neutral.
I’m not understanding what you’re asking here.
With an ungrounded system, really you could have a problem almost anywhere, but it will most likely be corrosion due to age. Could also be a busted receptacle that’s not allowing voltage to continue on.
If it’s a completely open neutral, you won’t get any voltage reading, as there will not be any ground reference, thus no difference in potential.
Don’t keep any loads on this circuit, by the way: if it is a corrosion problem then it is acting as a resistor, and like an electric heating element just sitting there heating up waiting to start a fire.
The two outlets that I pulled both have four wires total, 2 hot, 2 neutral. Each set going to a screw terminal.
My guess at this point is that the other working outlet in the adjacent room is not putting out 120V to the rest of the circuit. I will pull off that outlet and measure both sets. This won’t happen until tomorrow at this point though. Two dirnks and 120V with 15 amps is not a good idea!
Just to clarify: I should see 120 V for one pair going into the outlet, but some other number at the same outlet, but for the other set of hot/neutral.
I’m not understanding what you’re asking here.
With an ungrounded system, really you could have a problem almost anywhere, but it will most likely be corrosion due to age. Could also be a busted receptacle that’s not allowing voltage to continue on.
If it’s a completely open neutral, you won’t get any voltage reading, as there will not be any ground reference, thus no difference in potential.
Don’t keep any loads on this circuit, by the way: if it is a corrosion problem then it is acting as a resistor, and like an electric heating element just sitting there heating up waiting to start a fire.
Jeff
Ungrounded or floating neutrals can cause ghost or false voltages.
Op. Is it aluminum wiring? That can also cause resistive conditions in a circuit (read fire hazard) side note we aren’t allowed to go in and out of plugs here all wiring should be spliced and only one hot/neutral/ground to the plug.
The two outlets that I pulled both have four wires total, 2 hot, 2 neutral. Each set going to a screw terminal.
My guess at this point is that the other working outlet in the adjacent room is not putting out 120V to the rest of the circuit. I will pull off that outlet and measure both sets. This won’t happen until tomorrow at this point though. Two dirnks and 120V with 15 amps is not a good idea!
Touch a voltmeter to the screws where the wires connect at the outlet. Then stick the voltmeter leads into the slots on the outlet. If your getting 120v at the screws and not when sticking it into the slots on the outlet, outlet is bad.
Although, the fact your getting some voltage, but the wrong amount… not 120v, is why the suggestion is that you have a neutral issue. Strangely, neutral is really like a ground, since at the panel they connect to the same place as he ground on the ground bar. Although, you need the neutral to complete your circuit and when there is an issue with the neutral, it sometimes sends false voltages or carries voltage itself when tested with a voltmeter.
I bet a wire nut holding the whites lost a wire inside. Replace the wire nut with a GB wire nut with wings. They are the best. Use yellow wire nut when it’s connecting two wires, red for 3 or more wires.
The two outlets that I pulled both have four wires total, 2 hot, 2 neutral. Each set going to a screw terminal.
My guess at this point is that the other working outlet in the adjacent room is not putting out 120V to the rest of the circuit. I will pull off that outlet and measure both sets. This won’t happen until tomorrow at this point though. Two dirnks and 120V with 15 amps is not a good idea!
Yes, definitely start there: pull all the receptacles and switches that you know are on thst circuit (one at a time). You’ll find the problem!
Drinks and electricity go great together… fun to get your friends to intentionally shock themselves when they’ve get enough in 'em!
Hehehe…
Here is the best I can paraphrase from my son’s explanation of how to figure this out:
Find the breaker that kills the circuit the low voltage outlets are on.
Now look at what is dead and try to picture in your mind how the wire was run to connect all those receptacles. That is usually the most difficult part.
Now shut the breaker and check voltage in the each outlet going back towards the main box.
When you find an outlet that has full 120 volts. Stop
Kill the power and open that receptacle. Look at the connections for the wires. If there is an obvious problem fix it, you are done.
If there is no obvious problem, remove the receptacle and connect the black to black, white to white (or just connect everything on each side of the receptacle together)
Energize the circuit and go check the next receptacle. if you have power, the problem was inside the receptacle you just took out - replace it. If you still have a problem, do the same thing again at that receptacle. The problem is in that receptacle. Replace it.
He said that he is guessing that one of the neutral wires is no longer connect or the jumper tab is broken. Tug the wires and look at the jumper. He also said is not uncommon for the receptacle to crack internally and cause this problem. That is why you may need to jumper out the receptacle. Sometimes you can’t see the damage.
Good point: if there’s a load on the circuit, that could show a ghost voltage, as well, with an open neutral.
Where are you, Maurice?
Jeff
I’m in Kamloops (bc interior) having said that from what I have seen US and Canadian codes are largely cut/paste of each other. Best practices are largely unified across North America as most of our wiring products etc come from USA suppliers or parent companies.
Yes, they have been trying to get the NEC more standardized the last 20 year or so.
I remember hearing about places that were requiring receptacles be wired like that during my last code update, but think that was just localized addendums.
I should probably double check that here though… been a while since I’ve done any residential wiring.
Okay, pulled most of the other outlets: all measuring at 120V for both sets of wires.
I can’t be sure which circuit that the original dead one was on as I never mapped everything out when it was working. I pulled outlets in the adjacent room, the light switch in the adjacent room, and outlets at the next bedroom.
Nada.
So at this point to summarize: the two dead outlets are reading about 10V, the nearby light switch is not working, and all other outlets “nearby” are reading 120V from the backside, both pairs of hot/neutral. I guess I need to pull every outlet in this place…
Is this on the first floor? If so, is the basement open so you can see the wiring going up into the wall?
Making a lot of presumptions, but if you can trace the feed from the breakerbox to the first receptacle, start there. Receptacles are pretty damn cheap, so buy a bunch of new ones and start replacing everything (first one in the circuit needs to be a GFI if everything is ungrounded).
This turns you from a troubleshooter into a parts replacer, but at least things should be working after that.
If you really want to troubleshoot it and find the problem, start reading continuity on each individual wire from box to box (keep a drawing of everything as you go so you can track what’s what). Eventually, you’ll either find something open, find a bad receptacle or switch, or a bad splice.
If ypu go this route, you might as well replace all the receptacles anyhow. Shouldn’t take more than a few drinks… haha…
Thanks again for the advice. No basement here, pretty rare in Tucson. Yea, a continuity test across the wires is reasonable. I do not see another way to trace the lines without getting into the attic crawl space.
So, this is a rental and most are now thinking why not let the landlord deal with it. Yeah, maybe that is the right move, but waiting for him and his underlings to fix things can take a while.
