I used to participate a little on this forum as well as another, but have been out of the game for a few years due to health issues. Anyway, I'm wading back in and one of my first jobs is a real head scratcher. I received a call from a home owner about one bedroom in a house that is completely dead. I opened every outlet in the room to see if there was a broken or otherwise disconnected conductor, but found nothing to blame for the problem. I did the same for the adjacent rooms and the room directly below, but also found nothing. Part of my problem is that I don't know where this room is fed from. I was reading the topic on the toner and probe and was wondering if that could help me. Otherwise, anybody have any suggestions?
I try to look at those as if I were the guy doing the original installation, how I would have done it.
Some guys feed all the lights and drop to a plug and pick up the plugs in the room. Plugs on back-to-back walls are probably fed together. Did you remove the light?
Are the wires in all the boxes the same type? Maybe you have a hidden splice.
Has any work been done on the house? For example, I had a roofer cut a wire and do a poor job of the splice. Is there a long section of wall where a plug might have been covered over. Did you check for power on both sides of each plug that worked?
Did you check the breakers to see if one is dead?
Do you have continuity between ground and neutral? That might give you an indication of which way the panel is in the circuit.
You could short hot and neutral at a dead plug and trace continuity back toward the panel. That might narrow your search. If you get back to continuity in one direction and an untraceable wire in another, you will know what to disconnect when you re-feed.
A toner is a useful tool. Let's go back to basics, though.
First thing you need is an accurate 'map' of the house. Once you have that, go around the house and identify EVERYTHING. Identify the source of power for every receptacle, identify what every switch controls.
Besides making a drawing on paper, I also use colored masking tape to tag each cover plate. I start with blue, where I write the circuit #.
Once I have identified all I can, I go and check everything for proper operation. "Good" gets a bit of green masking tape. If there's a problem, a bit of red (get that mail order).
Finished with my 'survey,' I step back. Do I see any patterns?
Another tool in my arsenal is a 4-ft level. I set that against the wall at receptacle level, and I look for any bulges in the wall that might suggest a concealed box.
I look for signs of recent work, or repairs. I look for changes in texture. I try to guess how the building differs from its' original layout.
As a last resort, I'll power everything down and use a "data" toner to try to trace lines inside the walls.
Using these methods, I once was able to find several junction boxes that had been paved when a parking lot expanded. The boxes were about 6-ft away from the pavement edge.
The first thing I do is go to the panel and check/tighten every screw in the panel, breakers and neutrals. Do not skip over double pole breakers as you could be dealing with a multi-wire circuit. Also check that all the breakers are plugged in good, I once disassembled a dryer for a failure to heat only to find out the breaker was not plugged in properly, the motor would run but it would not heat. After that, its time to map out the house and look for hidden things. Just because a receptacle is hooked up do not count it as good, backwired receptacles can be hooked to the wire and still have enough corrosion and such on the contacts as to kill them, check every one of them with a meter, or a Wiggy if you have one on the truck. The toner can be a useful tool, just be sure to get a good one, some will not pick up through sheetrock or plaster. This is a tough one to dive back in on, good luck.
Life is tough, Life is tougher when you are stupid
I have done enough of these to where I can usually fix them in short order. First step is to try the sniffer to see if it's the hot or the neutral thats open. If it's the hot,run down all the breakers with a wiggy. Once the breakers are verified it is time to plug a lampholder into one of the "dead" sockets. Have a helper stay there and watch the lamp for a flicker as you go around to each receptacle, working or not, and plug in something and give the recep a good wiggle back and forth. I have a device holder that plugs into the recep and gives you a good handle to wiggle around with, but most anything will work. 9 times out of 10 we will find a loose backstab this way. Usually we get it so fast the customer is amazed, and sometimes shocked that we charge for a service call after 10 min of work!
If it's the neutral, same procedure in addition to checking contnuity from the non working string back to the panel.
In the unlikely event this does not turn up anything, then it's time to map it out as reno does. If we can't figure it out after an hour or two it's time to quote to re-feed the circuit, after determining where it was supposed to be fed from so that section can be abandoned.
The room in question was at the far end of the house from the panel, and even though there was only 6 outlets in the room it was on it's own circuit. I found that the hot conductor was loose at the breaker.
Once I had a panel, in which one hot screw obviously had never been tightened at all. Al wire too. All the other screws were rock solid. Thanks heaven this was a dedicated circuit that only fed the bathroom fan (only a fan, not a heater combo). I guess it had been that way ever since the 70s. All the outlets had loose screws too, but those were more like the typical Al woes.