Perplexing wiring

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Old 10-04-18, 07:42 PM
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Perplexing wiring

Hi,
I have a set of outlets that seem to have reverse polarity. I found a 'key' outlet, that when disconnected, disconnects all other outlets. When wiring it by itself, disconnecting the rest of the circuit, polarity is showing correctly. Then I add the rest of the circuit back in, and now that same outlet shows reverse polarity. Anyone have any idea of how an outlet can switch polarity without switching the wire that provides the power?
Originally I just thought I would switch the white an black wire, but there appears to not be any issue with the source wiring polarity. Thought I had a decent understanding of this, but I'm out of ideas.
I used two different device to identify the reversed polarity issue.
Thanks!
 
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Old 10-04-18, 07:58 PM
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Welcome to the forums.

Take the results of those plug-in testers with a grain of salt. They can show reverse polarity with an open neutral. The only true way to test is to use a meter. Even a basic analog meter is all that is needed.
 
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Old 10-04-18, 07:58 PM
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Unless you are mistaken due to faded wires (happens often with cloth wrapped wires), there must be a splice somewhere in between for that to happen.

Do you see any junction box with a blank cover?
Any lights that stops working when you disconnect the wiring at the outlet in question?
If not, there may be a splice made behind wall with or without junction box. Not allowed, but I see this all the time.
 
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Old 10-04-18, 08:28 PM
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Thanks. I am missing a ground as well for the circuit in question. I'm using an Extech Ct70 device to check, as well as a 'cheap' plug in. House was built in the late 70s, no cloth wire I'm aware of. All of these are somewhat inaccessible outlets, and I have not crawled into the crawlspace to check the wiring there, yet. Rest of house is fine. But I do believe that a wire (and outlet) was added in, not sure where, as another outlet in a newer wall is linked into the same.
 
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Old 10-05-18, 08:45 AM
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Without a ground, no tester can conclusively determine hot and neutral. The test procedure is to pull an extension cord from a known good ground and test between the ground hole of the cord and the unknown wiring in the wall. The hot (narrow slot) should be about 120V and the neutral (wide slot) should be close to zero.
 
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Old 10-05-18, 06:04 PM
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Thanks! That helps a lot!
 
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