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So I tested an outlet and I get 120v on Hot-Neutral and 0 on either Neutral-Ground or Hot-Ground. I found the previous outlet upstream (verified by disconnecting the hot and checking for power downstream). There, Hot-Ground gives 120v. So the setup is: Good outlet -> 3 light switch combo -> no ground outlet

I tested the light switch too between hot and ground and nothing.

I then went in the good outlet turned off the power and tested for continuity between the upstream hot and ground. The hot was separate disconnected but the grounds were spliced. I got it to beep.

So does this mean that somewhere downstream, the black is touching the ground? If so, how far downstream? If I am getting 0 on the light switch, am I correct to assume that it is happening there?

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“Continuity” between the upstream hot and ground can’t be a short between the black wire and ground. If it were, the breaker would trip and you’d have no power! This probably means that you have a light plugged into another outlet on the circuit and turned on. The low resistance of a light bulb looks like continuity to your tester. This is a red herring.

You have an open connection on the ground wire between the two outlets. It’s possible that the wire is broken but that is unlikely. More likely is a bad connection. Redo the connections on the two outlets. You might also try replacing the bad outlet.

If none if that helps, you’ll need to search for another box between the two. just because the bad outlet is downstream of the good one doesn’t mean it’s directly downstream. Look for another outlet or junction box that’s between the two. That’s probably where you’ll find your bad connection. Hopefully you don’t have a buried junction (against code),

If worst comes to worst, it is allowed by code to run a separate ground wire not following the original path. You still need to follow rules including protecting the wire. This would probably require a lot of drywall work.

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  • Thank you, at least this gives me some additional things to test
    – Michael
    Nov 4, 2023 at 14:32
  • A follow-up. If it turns out it is a faulty cable and I don't want to do any drywall work, can I put a GFCI in the upstream outlet that is grounded and mark the other outlet as gfci protected-no ground equipment?
    – Michael
    Nov 4, 2023 at 14:40
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    Nevermind. Found the culprit. There was a smoke alarm in between the good outlet and the ligth switch. I opened the box and of course they left the smoke alarm's ground bare (which makes sense since everything is plastic) but they also left the two ground unspliced. Left me barely enough space to splice them together. Another diyer I guess that doesn't bother doing a bit of research. Now I get proper, 120v hot to neutral and hot to ground and 0v for neutral and ground.
    – Michael
    Nov 4, 2023 at 17:09

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