I'm installing a gfci in a bathroom replacing a regular outlet. Initially it was tripping when the adjoining light switch was flipped. I moved that switch feed to the line side to fix that issue but my gfci tester shows ground fault error and will not trip the gfci when test is activated.

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    Do you have a ground wire? Picture of the wiring would help. Does the actual GFCI test button (as opposed to an external testing device) work? Jul 8, 2021 at 20:05
  • Thank you for the response. Yes, it is grounded appropriately. And yes, the test button on the outlet trips it off.
    – Scott
    Jul 8, 2021 at 21:17
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    Typical (but likely not 100%) situation of a GFCI tester not tripping a functioning GFCI is if the ground is not good, because the tester works by taking a bit of the hot current and routing it to ground (instead of to neutral). Picture of the wiring would still help. Jul 8, 2021 at 21:19
  • What is this "GFCI tester" gadget you're suing? Jul 8, 2021 at 23:47

1 Answer 1


Your GFCI tester is correct with an open ground it will not trip the GFCI

the test button on the receptacle will function, this is normal for a standard 2 wire circuit.

The GFCI won’t create a ground it detects an imbalance in the current between the hot and neutral, more than 5 milli amps or 5ma imbalance will trip the GFCI’s circuitry and turn off the power.

Why is the plug in tester not working? The plug in tester places a resistor from the hot leg to the ground lug and created a imbalance. No ground or open ground and the tester can’t create the imbalance.

Is your circuit safe? It could be. This is normal for a 2 wire circuit and as safe from electrical shock as a 3 wire protected by a GFCI.

If you have a true ground that is open you should find out where ground was lost. But if a 2 wire put the “no equipment ground” sticker on the receptacle and it is code compliant even in 2021.

  • I agree with this as the likely diagnosis and a good explanation. But OP in a comment said Yes, it is grounded appropriately. Jul 8, 2021 at 22:00
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    Yes, the OP did say that. That doesn’t mean it’s true. #1 you have to be skeptical about such judgements made by people asking questions like this (if they were actually qualified to make that judgment they wouldn’t be asking the question). #2 it’s also contradicted by the magic 8-ball measurements.
    – nobody
    Jul 8, 2021 at 22:45

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