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UPDATE - tested all the wires with a multimeter, WHITE - Neutral to GROUND - no reading, BLACK - Hot- to GROUND no reading, BLACK - Hot to WHITE Neutral no reading. When using a no contact voltage tester the WHITE - Neutral is beeping and giving me a warning, the BLACK - Hot isn't and so is the GROUND. I traced all the junctions and they are all wired correctly and tests correctly.

I just installed a GFCI outlet to an outdated backyard outlet that was just conventional outlet without any protection. Upon testing with an outlet tester, it reads 1-RED 2-Yellow 3-off hot and neutral reversed. I tested the outlet TEST and tripped successfully, and then RESET properly. Then I tested it again with the outlet tester and still reads the same 1-RED 2-Yellow 3-off hot and neutral reversed. Should I be concerned? What is causing this?

Some context, this is a 3 wire (hot, neutral and ground), when I turned off the breaker circuit for this line, its associated with the garage lights, half bath lights, and the backyard lights. I connected the wires to the LINE connections of the outlet.

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    Did you check the voltage of the wires with a multi meter to verify which is hot and neutral? You can't go by insulation color.
    – JACK
    Apr 10 at 18:51
  • No reading (based on everything else) on White (presumed hot) to Ground and Black to White makes no sense. Are you sure you are using the multimeter correctly (correct mode, correct connections if the meter has more than 2)? Test it against another receptacle. But non-contact lighting up only on White matches the hot/neutral reverse because that means White is hot. Apr 11 at 20:23
  • Yes, tested it on a different receptacle and is working, self tested it as well. It's on AC, V with ~ on top, probes were double checked and inserted firmly. I couldn't believe it either. The no contact tester reading the Neutral wire presumed hot may be indeed the issue here. I came to the conclusion this is beyond me now. It is not as easy as replacing a receptacle anymore. I am hiring a professional. Thanks for troubleshooting with me. Apr 11 at 20:32

2 Answers 2

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The three light testers are what Harper likes to call the Magic 8-ball. They give messages that are sometimes true, sometimes meaningless or even misleading. In this case, the message may actually be correct. What the message/lights you describe normally means is:

Klein RT110

(Note that the sequence and colors will vary by model of tester.)

  • Left red light = Voltage between neutral and ground (not good)
  • Middle yellow light = Voltage between hot and neutral (good)
  • Right yellow light = Voltage between hot and ground (good)

So when you have Red/Yellow/off, that means:

  • Voltage between neutral and ground, so one of those is connected to hot (Hot/Neutral Reverse or Hot/Ground Reverse)
  • Voltage between hot and neutral
  • No voltage between hot and ground (Hot/Neutral Reverse or Hot disconnected)

The only possibility in common is Hot/Neutral Reverse, so that's what the key displays.

The first question is: What did the tester show with the old receptacle? My guess is that it had no ground hole so you couldn't (super easily, though not that hard really) test it with the same tester, or maybe it had ground and you just didn't think of it. I bet it would have shown Hot/Neutral Reverse but we don't know that for sure.

Since a GFCI normally only looks at Hot and Neutral and ignores ground, a GFCI will still work (including TEST and RESET) with a Hot/Neutral Reverse.

So the most likely scenario is that you actually have Hot and Neutral Reversed! To test this, use a multimeter to check voltage between each pair of holes in the receptacle.

Klein MM300

If you get:

  • Hot to Neutral ~ 120V
  • Hot to Ground ~ 0V
  • Neutral to Ground ~ 120V

then you indeed have Hot/Neutral Reverse.

If you get something else, update your question and we'll figure it out.

If you have White to Line Hot and Black to Line Neutral on the GFCI then swap them. If you have Black to Line Hot and White to Line Neutral then the problem is at a previous receptacle or junction in the same circuit. I have found these reversals multiple places in my home from work done previously, presumably by the previous homeowner and not an electrician because that is Electrical Wiring 101.

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  • The old receptacle is indeed a three prong with ground except it is outdoors and not gfci which prompted me to change it since I plan to use that outlet for string lights and/or inflatable tub. I followed the same wiring diagram from the previously installed outlet. Hot/Black wire to Line Hot, and Neutral/White wire to Line Neutral. Bare copper wire to green/ground. The Old receptacle did show the same, Hot and Neutral Reversed Red/Yellow/Off. I did test everything before disassembly and replacement. I should test it with a multimeter and get back to you guys. Thank you. Apr 10 at 19:40
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    Clarifying question: I am testing with a multimeter and say a ground to neutral (white wire) is reading 120v, and ground to hot (black wire) is 0v, then what you're suggesting is that a previous receptacle in this same circuit was reversed. Now instead of me trailing it all the way back is it safe to just swap them? Apr 11 at 18:02
  • It is not safe to swap them because at least one prior receptacle has an actual problem. That problem may be on the incoming wires to that receptacle (what in a GFCI is called line) in which case that receptacle is also reversed, or it may be on the outgoing wires (what in a GFCI is called load) in which case it only affects this receptacle. But swapping when there is at least one reverse elsewhere is wrong. Or as they say, two wrongs don't make a right (but two Wrights make an airplane). Apr 11 at 18:43
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If the wires are actually reversed, then it is probable that they are interchanged at a junction point along the way.

It is probably not one continuous cable from the breaker panel to the outdoor receptacle. So follow it back and open each junction box to find the problem.

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