The "very small values" are meaningless. That's an artifact of using a high impedance DMM, which really isn't the right tool for the job. A simple rubber socket with pigtails from the hardware store, with a 25 watt bulb screwed into it, is a better tester for household electrical work.

It's hard to tell what's going on from your photo. You haven't shown all the wires that you describe. I see only the wirenut, not the taped splice. Please pull everything out of the box and take another photo.

IF all is as you describe, then nothing is wrong with the switch wiring. The top switch terminal looks loose, but that wouldn't affect the receptacles, just the light.

Your voltage measurements across the switch are as they should be.

Again taking your description, not the photo, one possibility is that the feed is from below, hot and neutral. The neutral and hot are carried on to somewhere else (probably through the ceiling junction box then on to who-knows-where) unswitched, A switched wire (red) presumably powers the light, which also taps the neutral (white) in the ceiling box.

Another possibility is that the feed is from the top, and the bottom goes on to something else, possibly your non-working receptacles.

Take apart the taped black-wire connection and probably also the white wirenut, and find out which black/white pair stays hot. Report back.

I can't be sure from the photo, but it looks as if your house may have been wired with conduit. Are you by any chance in Chicago?

I would suggest being very careful with those old wires, the insulation becomes brittle with age and will fall off. Years back a friend asked me to install a new light fixture, two days later I had rewired half the house.

Thanks, DavidR. Yes, the taped white (neutral?) wires are way back in the box, and I was reluctant to pull 'em out for the reasons mike suggested (so fragile!). For testing I've got a non-contact tracer, a plug attached to a lightbulb, and the DMM.

I turned off the breaker and figured out that the wires from the bottom of the box are hot. I have no idea where the wires from the top of the box go! This light is downstream of the hall and bathroom lights, and the non-working outlets (remember them?) are definitely not connected to the top of the box.

BUT, here's the fix we've settled on for now ( tell me how this sounds). I made a male--male power cable and ran it from a working outlet to one of the non-working outlets. Because all the non-working outlets are wired in parallel, they all now work. Problem "solved." Our theory (having now been up and down the stairs six million times) is that when a ground-floor wall was removed to install a washer/dryer, the feed to one of the outlets from the basement was severed and never replaced (it would have been easy for the old woman who lived here then, who never ventured upstairs anymore, to have missed that the outlets in one of the old bedrooms no longer functioned after the contractors left).

We're definitely wired w conduit--in Baltimore. House was built in 1938.

Thanks again.

Loren

Male-Male power cable aka Widow Maker lol

My advice, is get a pro in there to take care of wiring problems. Its an old house, and they are wonderful, but, the big problem is the wiring is very old too, and that is not wonderful. It is also possible, that there is knob and tube wiring in the walls of that house. Quite honestly, bad wiring is not a good thing to live with. It can be very dangerous. When the house was built, there were very minimal things to plug in. These days everything plugs in, which is why most people have 200 amp breaker boxes.

This is extremely useful. thanks. we actually spent the day yesterday tracing all the wires and opening all the boxes and outlets and switches on three floors--to learn more or trace other potential faults, we'd need to start tearing out walls. That was where we were _before_ the widowmaker solution (we don't have kids, and the killer cord is located in a closet and taped to the floor--still dangerous, for the reasons you cite, no doubt, though).

Realistically, we're not going to rewire everything on that feed--so we're left searching for a solution here that avoids the killer cord hack and also tries to reduce the "fireworks" risk of the original wiring unexpectedly re-connecting. Hiring an electrician would mean having the project done to code--that's not gonna happen right now (though we'd consider it if it were possible to have workers in the house, which it isn't), and we need those outlets to work.

There are many ways that we can get a feed to those outlets without using a killer cord, but none of them address the second risk ("fireworks") you mention. So far as I can think, _nothing_ will eliminate that second risk except rewiring everything on that feed (about which, see above--not the direction we can head right now). Why wouldn't the circuit breakers at the box trip if the loose connection (which I think doesn't still exist, but who knows?) reconnected? Isn't that why we rely on circuit breakers, generally? I can't brainstorm any way to insure that those outlets _aren't_ connected somewhere else inside the walls, even if we can confirm that all the wiring attached to the outlets themselves connects to the other outlets in the room...

thanks again to any who have the patience to offer advice.

Loren

@cat_ky, the house is wired with conduit. so far as we've found, there's no knob and tube (but fingers crossed)

When you can't see where anything is going, you trace electrically.

Some people recommend the Fox and Hound, an RF tracing device. I don't know how well it will work with conduit as I've never used it. I'm sure others here have.

I use an old fashioned approach. Start by drawing up a house plan with every receptacle, switch, and light in the house on it.

Power off! If you work circuit by circuit, be careful; once in a while you'll find more than one circuit in a single box, which can be an unpleasant surprise when you've opened only one breaker and think you have the power off. It's safer. if more hassle, to open the main breaker.

Remove all the devices (receptacles, switches, light fixtures) on the circuit - in your case it might have to be a good part of the house - and scout out each connection from box to box.

For testing, you can use your continuity tester with a long, long wire clipped to one test probe, or even just wrapped around it with a wirenut added.

However, my preference is a low voltage test light. I used to use a 6 volt screw-post lantern battery for the power source, when they were common in hardware stores. Now that those are hard to find, I have a 4-cell D-cell holder with 4' or so long clip leads attached. You want a relatively low current source for safety, in case you accidentally connect to a short circuit

My tracer is a flashlight bulb screwed into a miniature socket with pigtails.

You can probably buy something similar to my homemade setup, but I haven't looked.

Connect the battery to a pair of wires to test. You can probably connect to a single wire and to the metal box or the conduit, if you're sure that all of your house is wired with conduit and it has a solid path between boxes. Then poke around in the other boxes nearby until you get a light.

As you test, fill in the connections between boxes (and eventually to the main panel) on your house drawing. At some point, you'll look at your drawing and say to yourself, "I see where the problem is. How did I miss that before?"

@DavidR, this is so useful. THANK YOU for taking the time to write this detailed reply and share your knowledge. If we do this, it might be worth replacing all the old non-grounded outlets with grounded ones (assuming we can get a decent ground connection without pulling new wiring). If we confirm that the conduit is connected throughout the house (which we could easily do if we're using my homemade version of the 6volt tester you describe), can we ground to that?

@DavidR, circling back. spent days doing all the tracing and then chased a new piece of Romex through the walls to rewire all those plugs on the second floor (duplex outlets replaced with grounded ones). All tied to a new Square D 20amp breaker. I'm told it's all to code, by the electrician that talked me through it over the course of a couple days from his boat in the Caribbean. Slowly and methodically putting the baseboards back on, repainting trim, etc.etc. Thanks again for your help--turns out we're wired w BX (which some folks call "conduit" here in Baltimore), and yes, you can use it as a ground, it turns out.

Funny, we just had a thread about that recently. If what you have is genuine BX, DO NOT use it as a ground. It's a fire hazard! You're better off with no ground at all than with a BX ground.

The problem is that after years, the armor on BX corrodes, and no longer makes good contact between coils. Its resistance increases. If ground fault current goes through it, instead of tripping the breaker or blowing the fuse, it can heat the armor up just like the heating element in a toaster. This has caused house fires.

If there's no ground wire in that stuff, please don't try to ground your receptacles. Install GFIs instead, and mark them "No Equipment Ground." I use Brother stick-on labels for labeling. GFIs get you improved safety without a ground.

Other than that, I'm glad to hear you solved your problem!

David is right (other than the fact that it's not even necessary for corrosion to be present to have the ground issues with the BX armor).

I worked electrical in Baltimore (well Baltimore and Harford counties) for years. I've never heard anybody call armored cable CONDUIT. We've got lots of funny words and pronunciations in Baltimore, but that's not one I ever heard of.

Hmm. Opinions seem to vary on the BX-as-ground issue. What about grounding to the pipes that carry hot water to the radiators? I'm imagining connecting, say, one fixture on each breaker to a pipe, which would mean that the majority of the path from any failing fixture to ground would run along those pipes (everything "downstream" of the one fixture per breaker tied into the heating pipes would still depend on the BX to get ground to the one designated fixture electrically tied to the pipes). Not a perfect solution (because some BX still in the ground path), but better? I'm not about to rewire the whole house w Romex...

Useful thread corroborating the safety of the use of GFIs in the absence of a house ground (third wire). https://forum.nachi.org/t/gfcis-and-ungrounded-receptacles/70237/27

I wouldn't do that. My recommendation is that you install GFIs for now, and start tucking away the pennies for a full rewiring job.

While you're saving up, get a copy of a good book on wiring and start reading. I recommend Ray Mullin's Electrical Wiring Residential. Start with some relatively small jobs -- say, rewiring the laundry room -- and you may find that by doing most of the rewiring yourself, your cost and bank account curves will cross.

Afterthoughts: There's a good argument for starting with the kitchen, but it's relatively complex. I'm an old house guy, and a geek, so I prefer to start with my home office. That way, I have a proper circuit for my computers. :)

Properly installed and labeled GFIs would make rewiring unnecessary, though, right? Maryland home inspectors indicate that this is an acceptable solution, right? Thanks for the book rec.

I wouldn't say that GFIs make rewiring unnecessary, but they do take care of the human safety factor where no safe ground is available.

I rewire my offices first because I want clean power for the computers, and a proper ground for surge suppressors.

The other thing that a good rewiring job does for you is expand the number of circuits and receptacles available. That gets rid of most extension cords, and reduces overloading problems. One reason that I mentioned the kitchen is that most kitchens with wiring from the 1970s and earlier aren't up to today's appliance usage.

"Radiators" are not themselves a legitimate ground. The operative stuff is in Art. 250.130. Your heating and water pipes, while required to be bonded to the building ground system, are not legal substitutes for a ground for grounding branch circuits. The only time a piping is a part of a legitimate ground system is the first five feet of where a metal pipe enters a building from underground.

You can connect to a different branch circuits ground (if it has one), or to some accessible part of the buildings ground system (ground rods, or the water pipe within the first 5 feet). Other than that a GFCI will allow you to plug in grounded plugs with occupant safety, but as DavidR points out, that the surge protection is enhanced when there's a real ground there.

very useful. thanks. why do you think this rule exists? "Your heating and water pipes, while required to be bonded to the building ground system, are not legal substitutes for a ground for grounding branch circuits. The only time a piping is a part of a legitimate ground system is the first five feet of where a metal pipe enters a building from underground."

I think - and I trust that Ron will correct me if this is wrong - that it's because if the pipe system's bonding should fail or become insufficient, the piping would become energized in the event of a ground fault. That would make it an electrocution hazard.

You can run a separate green-insulated ground wire back to the main panel from each receptacle, but if you're going to go to that much trouble, you might as well run new cable the same distance. Assuming that your local code allows NM, that is.

heh. GFIs it is, then.

Hi there! Just wondering- did you use 12-2 Romex or 14-2 Romex for your new circuit?

The reason I say that is because it is almost verbatim from the code. That's enough justification to NOT do it.

The reason the code states that is that as David points out, while metal piping is required to be grounded, it may not be done well enough to serve as an adequate ground. For example, domestic hot water pipes and pipes coming out of boilers may have had a dielectric union installed to forstall other (plumbing corrosion) issues which means they're not bonded. It's also possible someone sticks some section of non-conductive pipe in and didn't rebond the 'orphaned' piece of metal, etc...