Mixed signals when testing GFCI outlets

So im at this 1969 condo and when i plug my tester into the two bathroom outlets, it initially tests as correctly wired, then when I hit the GFCI Test button, it not only does not trip, but the signal changes to “hot/neutral reversed”.

Can someone explain to me whats going on here? very little experience with older electrical systems

Welcome to our forum, Michael!..Enjoy! :smile:

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Michael did you try it with another tester?

Thank you! glad to finally make an account and participate.

No, only had one. But this same thing has happened on another older house I’ve been at.

Reverse polarity. Since testers establish a test circuit between hot and equipment ground, if the receptacle into which the tester is plugged is wired with reverse polarity, there will not be a voltage across the tester and test current will not flow. The GFCI will not trip and thus the GFCI might erroneously be considered defective.

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The three prong tester will do that if there isn’t a ground.

Should this happen considering the above quote though?

if there is no equipment ground You can get those results…did You pull a device out and count the wires?

It sounds like a bootleg ground, which will fool a 3-light tester.


Was the middle bulb brighter?
Pic please.

In any event. Follow up with a non-contact volt tester to measure stay voltage.

I agree with Christopher, IMHO.

why put a bootleg ground on a GFCI that will work just fine with no ground?


Not everyone knows that, Bob.

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Am I correct that if it is a bootleg ground, the tester should still trip the GFCI? Or is that not correct?

No, the signal changes to “hot/neutral reversed”. LOL!

I guess that does make sense. The GFCI does not know the return current on the neutral is coming from the bootlegged ground.

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It hasn’t in my experience. There’s not a true ground. The test button on the 3-light tester would just send current back down the neutral, and not trip the GFCI.

I would think it would still trip. The tester essentially shorts the hot lead to ground when the button is pressed (on the tester). The current flow trips the GFCI. If you shorted the hot to neutral you would have the same current flow and the GFCI should trip because that is what happens when you press the test button on the GFCI (it will trip itself with no ground).

I have had this happen in a newer home recently. It turned out to be just a bad GFCI.

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Pushing the GFCI test button will cause a small (10ma) amount of leakage between hot and safety ground. Any common 8ma GFCI devices upstream of this point will trip.

If there is no GFCI upstream, the GFCI will not trip because it doesn’t exist. The overcurrent protection device (the breaker) will not trip because it isn’t a GFCI device and 10ma is not anywhere near an overcurrent.

If the receptacle is not grounded, the upstream GFCI will not trip because the intended 10ma of leakage is going from hot to nowhere. Since current flows in loops, it won’t flow. In that case, you test the upstream device using its own button and make sure this outlet loses power.