Thread: Why all 3 lights of circuit tester are on

This is a LEVITON 15A-125V receptacle above a wood-burning fireplace of a 80 years old house. Probably this receptacle is for an electric clock. When I plug in a circuit tester, all 3 lights turn on. What is the problem on the wiring and how to fix it?

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Reversed hot and neutral with an open neutral or high resistance neutral connection will light the red full bright and the 2 yellows dim, but noticeable.

These 3 light testers can lie to you. Buy and learn how to use an analog (swinging needle type) meter or Wiggy.

Originally Posted by Daniel Leung

This is a LEVITON 15A-125V receptacle above a wood-burning fireplace of a 80 years old house. Probably this receptacle is for an electric clock. When I plug in a circuit tester, all 3 lights turn on. What is the problem on the wiring and how to fix it?

Check the outlet with a volt meter. When all three lights are on when I plug my tester into an outlet, I typically find that the 120 volt receptacle outlet is wired with 240 volts.

Originally Posted by Gunnar Alquist

Check the outlet with a volt meter. When all three lights are on when I plug my tester into an outlet, I typically find that the 120 volt receptacle outlet is wired with 240 volts.

GA: My, how time flies!

Dan:

My testing device did the smae thing in the field so I actually tested this out with a receptacle purposely wired incorrectly in my shop.

The only situation in a 110 volt receptacle that got this testing was to have a hot/neutral reverse and open ground. It may seem inplausible since an open ground by itself gets only one yellow light on the testing device, but that is what got the result.

If you are not sure how your 3-light tester displays 240v or the now mentioned reverse N-H and open G, check any unusual indications with a VOM.

More info on this thread 3-light circuit tester

Daniel Leung, if your an inspector, of checking electrical wiring for a living
you need to invest money into a professional model. And even they can
give false readings is somethings in plug into the same circuit that the
receptacle your testing is connected to. GOOD LUCK!

Originally Posted by Vern Heiler

If you are not sure how your 3-light tester displays 240v or the now mentioned reverse N-H and open G, check any unusual indications with a VOM.

More info on this thread 3-light circuit tester

Vern and all, Thank you for the posted thread that I missed even I did search the forum. I have my multimeter/VOM (volt-ohm-milliemmeter) in my bag and know how to use it (see this thread) but I only use it on the countertop receptacle in kitchen. I am not an electrician, but I think the 3-light circuit tester still a good tool for primary test, and a 110-220V voltage tester or a VOM should be follow if in doubt.

Originally Posted by Daniel Leung

Vern and all, Thank you for the posted thread that I missed even I did search the forum. I have my multimeter/VOM (volt-ohm-milliemmeter) in my bag and know how to use it (see this thread) but I only use it on the countertop receptacle in kitchen. I am not an electrician, but I think the 3-light circuit tester still a good tool for primary test, and a 110-220V voltage tester or a VOM should be follow if in doubt.

DL: Agreed. They are sufficient for preliminary testing. Bigger guns should be available in reserve in order to ferret out the unusual.

Originally Posted by Daniel Leung

This is a LEVITON 15A-125V receptacle above a wood-burning fireplace of a 80 years old house. Probably this receptacle is for an electric clock. When I plug in a circuit tester, all 3 lights turn on. What is the problem on the wiring and how to fix it?

Originally Posted by Daniel Leung

I have my multimeter/VOM (volt-ohm-milliemmeter) in my bag and know how to use it (see this thread) but I only use it on the countertop receptacle in kitchen. I am not an electrician, but I think the 3-light circuit tester still a good tool for primary test, and a 110-220V voltage tester or a VOM should be follow if in doubt.

Daniel,

Excellent, ... so, how did that turn out when you measured it with your VOM multimeter? What voltages where were?

Originally Posted by Jerry Peck

how did that turn out when you measured it with your VOM multimeter? What voltages where were?

JP, As mentained before, I only use VOM in kitchen, so I just wrote down "faulty wiring receptacle' on my report and missed the chance to check the voltage on this receptacle. But I learn a lesson from this case: If all 3-lights on again, I will do a VOM test to confirm.
Anyway, I will go back to the house and do VOM test later. Thank you for the advice, you are our HI mentor!

Hi Daniel,

How did this turn out?

Hi Randy,

It was three years ago, when I went back to the house. The owner already removed the receptacle above the fireplace and covered the opening with drywall by a handyman.

Originally Posted by Daniel Leung

Hi Randy,

It was three years ago, when I went back to the house. The owner already removed the receptacle above the fireplace and covered the opening with drywall by a handyman.

He probably concealed the junction box behind the drywall. That is a violation of the CEC and I'm sure, the NEC, Even worse, there may have been an open neutral in that mess, discovered by your tester, now hidden in the wall.

When I find an outlet where all 3 lights of the tester come on, I may not know what's wrong, but I do know it ain't right, and I just report it as such, recommending correction by a licensed electrician, and move on.

I had one last week that tested okay when the adjacent wall switch was turned on, but then showed the hot and grounds being reversed when the switch was turned off. Talk about doing a double take! This was a house with extensive Harry Homeowner "improvements", and you can bet I recommended correction by a licensed electrician.

I have two receptacle testers I made which cannot be fooled with those mis-wiring issues. I made these about 10 or so years ago.

Each measures the voltage between hot and neutral, and between hot and ground, and between neutral and ground. You can see at a glance that all is okay.

When using the digital one, you just have to be careful to check that it is not showing mili-volts when it shows a reading.

That's a pretty good idea! I particularly like the male plug pigtail that can be replaced when a tight receptacle either pushed the ground lug back or pulls it out.