Built in receptacle test button didn’t trip, but 3 bulbs tester DID trip it

As I learnt somewhere on this forum it’s always better to use a receptacle’s built in GFCI test button to test a receptacle, rather than our 3 bulb testers trip button.

Now I know that if the 3 bulb tester doesn’t trip the receptacle, but the built in one DOES trip, it probably means no ground, and if the manufacture’s button trips and cuts power, we are good. Just no ground.

But how about the opposite? The GFCI’s built in test button did NOT trip the receptacle. However, my 3 bulb tester DID trip it. Now I know it doesn’t make a difference at this point, the manufactured test failed so the GFCI is no good. But I’m trying to learn something from this, what condition would cause this?

And I would say it’s a good proof that I should always try the built in tester, and not just rely on the 3 bulb. ( A Klein RT310 also tripped it)

Thank you.

Did the tester show that the receptacle was correctly wired?

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Yes, thanks for any help!

I used to have a schematic for GFCIs but I can’t seem to locate it. Logic would suggest it is a fault with the test button itself and not the sensing circuit. It did sense a change in current with the three light tester and tripped, but not with the test button. If I remember correctly the test button places a resistor across the hot / neutral and the sensing circuit (which trips the GFCI) senses the current change. The three light tester does something similar but applies the load resistor to the ground. Be interesting to know how a suretest trips it. I would definitely call it out, the test button is what the client will use.


I had one do that once before. After I it tripped with my tester, the receptacle test button worked. :confused:

The testers are for inspectors to verify that a receptacle is GFCI protected not that the GFCI operates properly

Excellent point Michael Parks, I think many of us forget that the hand held tester doesn’t test the outlet, just the circuit and wiring. The test button on the outlet is what tests the GFCI outlet and determines if the outlet is bad.

He won’t hear you… … …

Wrong! The tester just arrives at its results differently. The Sure Test uses the ground lead and will report mv to trip that should match the manufacturers specs.

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