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I've moved into a 1950s house and there are a few outlets reporting an open ground (per my Gardner Bender GFI-3501 tester) . I've followed the circuit as best I can but I'm in over my head. I've created a wiring diagram to show everything I've found so far.

There's a box with two 3-way switches that are pigtailed. When that pigtail is disconnected, the outlets report correct. I believe that implies the problem lies in the "post-pigtail" part of the circuit, but I'm just not knowledgable enough to know where it is.

Any help is greatly appreciated!

Original diagram: Original Wiring Diagram

Updated diagram: Updated Wiring Diagram

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  • What model tester are you using? Are the blue neutrals actually white? Oct 12, 2022 at 21:33
  • Do you have a multimeter? If so, get voltage readings on hot/neutral, hot/ground, ground/neutral of the problem receptacles. Oct 12, 2022 at 22:24
  • Carefully revisit the wiring in the "dining room switch". There is a black wire you have not accounted for. Also, the "stairway switch" seems to be a mystery. Where is the wiring to the stairway light? Oct 12, 2022 at 22:45
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    @manassehkatz-Moving2Codidact The tester is a Gardner Bender. I believe it's this model. Yes, the blue neutrals are actually white wires.
    – Zach
    Oct 12, 2022 at 23:16
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    @Zach OK I had no idea those were 3-way switches on the right because they are wired completely wrong. Do you actually get 3-way behavior, meaning that you can turn off the Dining light from the Stairway, then walk to the Dining switch and turn the light back on? Oct 13, 2022 at 1:21

2 Answers 2

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Nice diagrams. That will help.

Based on the Updated Diagram:

The unidentified "neutral" wire on the Dining Room Light appears to be something other than this circuit's neutral conductor. It might not be a neutral wire at all, in which case the light can only work when faulted to ground. You'll need a multi-meter, at least, to find out how much voltage is on the light and switch wires. If you still can't figure out what's going on, you might need to take apart the switch connections and take down the dining room light too.

With that same multi-meter, find out exactly what's happening with the "open ground" receptacles. Is there any voltage between ground and neutral? Hot and ground? If you run an extension cord from another circuit, is there voltage between the ground or neutral wires of the two circuits?

The Hallway Switch is connected wrong. If the neutral wire enters from the bedroom, it must continue on to the stairway as well and must be present in the cable used there. This means the incoming hot wire must be connected to the hallway switch, or you don't have enough wires run between the hallway and the stairway junctions. It isn't possible to have one hot, two travellers, and one neutral wire in a /3 cable. It just doesn't add up.

For reference, NEC 300.3(B) "where used, the grounded conductor ... shall be contained within the same ... cable or cord unless otherwise permitted"

More than likely you need to do one of these things:

  • Use a smart switch solution that requires one or zero travelers.

OR

  • Run more wire from the hallway to the stairway to the dining room.

As an extra safety measure, you could replace the "Bedroom Outlet" with a GFCI receptacle, make sure the "Power Source" works normally on the line side of the GFCI without the red wire, and then pigtail the rest of the circuit to the load side of the GFCI.

I also encourage you to improve the grounding on this circuit. From the photos, it looks as though several of the ground wires are loosely wrapped around the cable clamp screws and are not properly spliced to any of the switches. The Hallway receptacle looks excellent, the others do not. Adding bare or green pigtails and putting all the ground wires into a wire nut at each box should add some sense of extra safety for you.

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  • Thank you for your response. I'll try to get some photos tomorrow to help clarify so I can respond to each of your points.
    – Zach
    Oct 12, 2022 at 23:32
  • @Zach Excellent work on these diagrams. I've updated my answer. Basically, you're going to need a multi-meter, and try to figure out if there's a missing piece to this puzzle, or is the dining room light simply not connected to the circuit's neutral? Oct 14, 2022 at 1:32
  • Thanks again for all the info. I have a much better understanding of this circuit now and have some direction for my next steps.
    – Zach
    Oct 15, 2022 at 0:51
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The first rule of grounds is - grounds are never at fault.

Lots of people find they can make their system work better if they interrupt a ground. In those cases, they are looking at the problem upside-down: there's nothing wrong with the grounding; the issue is something else and they need to look at the something-else.

The first rule of 3-light testers is they lie.

Well, the lights are telling the truth. The labels lie. The label text is written for incorrect wiring in brand new construction -- not correct, but failed wiring in old work. Thus the advice is wildly, comically wrong! We've even seen people exchange hot and ground wires on every receptacle in the circuit, because the tester told them to, even though that's suicide. Don't get sucked into that kind of thing.

Also, make sure you are reading the indication correctly. Don't interpret "1 yellow" as "open ground" - it may also mean an open neutral under certain circumstances.

Notes on your setup

The /3+ground cable between bedroom switch and bedroom outlet was put there to allow the receptacle to be switched from the light switch. It appears to be currently wired to be NOT switched, and that's good because putting a receptacle on a dimmer is unsafe and illegal.

The /3+ground cable from bedroom switch to light was provided to allow a ceiling fan up there. The red and black hot wires could be used either for dual switch control of light and fan; or switched light and always-hot for a pull-switch controlled fan. Code requires a light switch in the room to turn on a light in the room (or a receptacle but again, not allowed with a dimmer).

The /3 cable between hallway switch and stairway switch box is because it is a 3-way circuit. It is wired like this, with the stairway-end switch being a "spur switch". No other wires should attach to that switch.

enter image description here

Red is switched-hot. Yellow is the 2 travelers.

The right hand switch box has an undocumented black wire. I suspect that black + the mystery white, is power supply coming from a completely different direction and possibly from a different breaker. That makes the hot jumper at the 3-way downright dangerous - if circuit breakers happened to be rearranged in the panel, 50/50 chance there'd be 240V across those two hot sources, and the jumper would go KA-BANG!

Insofar as I can tell from the picture, the undocumented black wire has been destroyed for some reason. Someone has jury-rigged it to bring "neutral only" from another circuit or part of the circuit. This violates the "all related wires in same cable" aka "tree cable topology" rule, NEC 300.3. If the black and ground wire can be reached somehow and pulled into the box, it can be a player. Otherwise the neutral must be disconnected and not used.

So that explains the odd jumper, the person is for some reason taking hot from one place and taking neutral from elsewhere. Not allowed.

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  • Thanks for the info. I should have clarified that the "Bedroom Light" is actually a "Bedroom Light/Fan". Another comment suggested the diagram is missing a black wire in the Dining Room Switch box as well, so I will double check.
    – Zach
    Oct 12, 2022 at 23:38
  • Ok, that makes sense. I will see if that black & ground wires can be reached on that cable. I’ll also look into NEC 300.3. I appreciate your help!
    – Zach
    Oct 15, 2022 at 0:53

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