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Preface to OP: I am a dope. The reason the GFCI does not trip when I push the "test" button is because the GFCI has failed. That's the whole point of the "test" button. End of story. Read on only if you want more details about how the things work.

I've noticed a GFCI outlet in which the "test" button depresses but does not cause a trip. Pressing the "reset" button temporarily disables the outlet, until it is released (which may be normal behavior).

I don't have a GFCI tester, so I tested it by shorting a 10K resistor between hot & ground. That's 12ma or so, which appears to be well over a typical trip threshold; and I've tried it on newer ones (elsewhere in the house) and it trips them just fine.

Furthermore, I have TWO GFCI outlets that are exhibiting this exact same behavior. However, they are the same brand and were installed when the house was built 32 years ago. Is this a known failure mode ? Seems like the problems most everyone reports are needless trips.

P.S. They were not wired incorrectly (e.g. "hot" to "load" terminals).

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    A 32 year old GFCI doesn’t owe you anything... – Harper - Reinstate Monica Aug 1 '19 at 5:54
  • For like $5 you can get an external GFCI tester (usually combined with "3-light-tester" functionality) and not be goofing around with a bare resistor lead connected to the hot line. That sort of casual cowboy BS eventually tends to buck you off, sometimes hard, and is really not a good idea for the price. – Ecnerwal Aug 2 '19 at 3:34
  • Thanks for your concern Lawrence. You probably have a point, but if it makes you feel any better I (1) used insulated pliers, (2) always wear rubber-soled footwear when doing electrical work, (3) know to never use both hands (if they could conceivably come into contact with wiring). – RustyShackleford Aug 2 '19 at 19:28
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This can happen, just replace the GFCI outlets in question

The TEST button on a GFCI creates an actual ground fault (about 6-8mA, maybe up to 10mA, from load-hot to line-neutral or vice versa), so if a GFCI fails to trip when the TEST button is pressed, then it's dead and needs to be replaced. This can happen due to improper wiring (backfeeding a GFCI's LOAD terminals will burn out the trip solenoid), or more commonly due to damage to the GFCI's (largely analog!!) electronics package caused by mains surges and spikes. (More modern GFCI designs may have a varistor connected across line-hot and line-neutral to help protect the electronics from surges, but this is by no means guaranteed.)

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  • I'll check for back-feeding (not super impressed with the guys who wired this house, non-GFCI protected lighting fixture in walk-in shower, for example), but anyhow sounds like they're dead. Funny they both seem to have the exact same symptoms ... – RustyShackleford Aug 1 '19 at 4:33
  • @RustyShackleford -- load-hot to ground should trip it, load-hot to load-neutral shouldn't because that's the intended path for current to flow :) – ThreePhaseEel Aug 1 '19 at 11:40
  • Duh, I meant my 10K resistor went from load-hot to ground. – RustyShackleford Aug 1 '19 at 19:05
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This is exactly WHY there is a TEST button.

The TEST button is so that you can "test" the device. There are known failure modes, and because this is a life-safety device, testing is important. Many newer GFCI devices actually have automatic testing since most people don't bother with monthly (or yearly) tests of their GFCI devices. The automatic testing effectively (if it all works...) turns the device from a fail deadly (i.e., always "on" so failure is failure to turn off = deadly if there is a ground fault) into a fail safe mode (i.e., the automatic testing simulates a ground fault and if that fails then it will turn off, so that there is very little possibility of "on and not able to turn off when there is an actual ground fault").

How much electronic equipment do you have that lasts 32 years? Are you using the same TV, computer, smoke detector or any other sophisticated electronic device that you used 32 years ago? GFCIs are relatively simple, but they do wear out, just like most other electronic items. Unlike most, they have a test button. Actually, your smoke detectors also have test buttons, but now they are designed to be replaced after 10 years whether you like it or not - because too often the detector mechanism or other parts fail and too many people don't bother to test.

Nuisance trips are sometimes a too-sensitive or otherwise failing GFCI. More often they are appliances or other devices plugged into the GFCI circuit that actually have a ground fault.

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  • Why on earth am I allowed to edit your answer, that's weird - my mistake. – RustyShackleford Aug 1 '19 at 4:45
  • I don't trust the "test" button on smoke detectors and use a stick of incense instead; or the CO detector for that matter. – RustyShackleford Aug 1 '19 at 4:46
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    But yeah, pretty crazy I haven't hit the test button on these GFCI's in like ... 32 years. – RustyShackleford Aug 1 '19 at 4:47
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    You can edit my answer because that's a "thing" is StackExchange - but if I don't like the edit I can bounce it back. I'm constantly editing other people's questions & answers for spelling & grammar & images, etc. – manassehkatz-Moving 2 Codidact Aug 1 '19 at 4:58
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    Duh, per first sentence of your answer. Guess I was expecting the TEST button to click into place, like on a working unit, but the click I expected is actually the solenoid. – RustyShackleford Aug 1 '19 at 19:08

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