I've just moved into a new (Australian) house, and I've been checking the outlets with this. Deta outlet tester

On one of the outlets all three of the lamps go on when the outlet is switched off. When you switch the outlet on, the blue lamp goes off. As you can see from the card, it's not useful for telling me what's going on.

Can anyone tell me what this means, and how concerned I should be? I assume it's been like that for the 20 years that the previous occupants resided here, and they're all still alive.

  • what's on the back of the card? – jsotola Jan 31 '19 at 3:25

The live and neutral are probably reversed.

Googled images of testers and found this.


The red in the image is also red on your card.

enter image description here

  • That's a magic 8-ball tester, so named because the legends are complete rubbish. The lights are fine. And are similar to the Aussie device. – Harper - Reinstate Monica Jan 31 '19 at 5:11
  • Got a real electrician in with a better tester and that was exactly the problem. He looked disappointed by the previous work.. – Spike Jan 31 '19 at 22:39

Sounds like they have both swapped hot and neutral, and they are switching neutral. This is probably one mistake, made in the switch area.

This device is simple: the green light is between hot and neutral. The blue light is between hot and earth. The red light is between neutral and earth.

The device has a useful feature: it deliberately doesn't try to explain the meaning of every color combination. That's because there can be several reasons for any of them. And as such, anything they say is likely to be balderdash and more misleading than helpful. This drives us crazy with the similar tool in North America; some of us call it the "magic 8-ball" tester because their explanations of the cause are so laughably wrong, and waste a lot of time.

On safety, raises hands yeah, you got us. The system is overbuilt so it takes more than one simple failure to create a hazardous condition. All this stuff is redundant. Fuses, your system will work without em. Grounds -- well, you need them on that circuit, but not normally. Yeah, so shortcut away. What could possibly go wrong?

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