I've been doing some reading on this forum, learned quite a few things, and this is my first post!

First off, I am decent with DC circuitry but a total noob when it comes to home (AC) electrical. Also, English is my second language so I hope the terms are right and clear :)

I'm having an issue which will require a qualified electrician to fix, but I would really like to understand what and how it's happening.

The issue;

Very old house, wiring certainly not up to code. I wanted to replace an outlet in the garage that's causing slight shock when using a metallic power tool and touching my metal work table. Before going through I did verify using an outlet on a different circuit and the the issue is not present. After switching off the panel breaker and making sure the power was off I removed the outlet and did not see any damaged wire that could make a short or cause an issue. I only realized that it was a mess since there were 6 wires plugged to the terminals of the outlet, white and black mixed together, no ground wire -apart from a connection that was added to one of the light switches-..damn

This outlet connects to two light switches (three way) and the circuit bringing the power to the outlet also powers a part of the house (wow..).

I installed a GFCI outlet to make things a BIT safer, it works, but I still have the same issue, power to ground (?) -bought a non-contact circuit tester to make my life easier, yay-. Took the time to check with the tester and ended up with weird results;

The outlet box itself, both switches box in the garage, are all HOT (they all make my pretty accurate tester beep) How can this be possible? Two boxes have a cable with ground connecting them, I could understand, but the third one use a 2 wire cable connecting it to the outlet.

For now the breaker remains off, I need to get a quote from a QUALIFIED professional, but I'm puzzled and would like to understand the issue.

Thanks for your time, and sorry for the long read!!

Update; Took some measurements yesterday after work at the outlet;

Hot(blk) to box .2V Return (white) to box 1.0V Hot to return 120v (118~)

Obviously box is not grounded.

Used an extension from a recently installed outlet with working ground.

Hot to grnd 120v return to grnt 0v box to grnd 1v

Interestingly enough, without anything plugged in the outlet, if I measure voltage between working ground and outlet housing/cage (where it screws to electrical box) i get Ov, but if i plug something in, i get 36V!

Also, I realized the light fixture in the ceiling is wired wrong (reverse polarity).. Unplugged this circuit from the outlet connection but I still have the shock hazard issue.

Sorry I cannot upload pictures as they are over 2mb and cant edit at the moment

  • 2
    Pictures of all the relevant boxes showing the wiring would help. Nov 9, 2022 at 17:04
  • 1
    Non contact testers usually only good to check if no power near them. The box is probably not hot(as in a hot wire connected to it), but close to hot power. A meter would be able to test if the box is truly hot.
    – crip659
    Nov 9, 2022 at 18:20
  • 1
    We are not sure about the accuracy of the non contact tester. They can report Hot from an inch away from the wire.
    – Ruskes
    Nov 9, 2022 at 18:26
  • 1
    @Ruskes indeed, I have a multimeter with non-contact test mode, and just waving the test probe end in the general vicinity of live wires causes it to beep. That's the point of non-contact test mode, of course. If I wanted to know which wire is live that's what the rest of the meter is for.
    – user253751
    Nov 9, 2022 at 19:11
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    @RUSKES ; I bought a Klein tester, tried it before the job and it's very accurate, to the point i can see which side of an extension cord has the HOT vs return wire. Which is quite surprising seeing the end result.
    – Nathan
    Nov 9, 2022 at 21:37

1 Answer 1


Even if you hire this stuff done, it's really valuable to be able to see for yourself that it is correct.

As such, I'd like to recommend you look at a few books on home wiring at your local library, bookstore or home store. Find one that feels accessible and read it through as you get a chance.

It's important to use books, and not Google, because books give you a well-rounded primer on the subject. Google only answers questions; it doesn't tell you which questions to ask. And much worse for you, experience with DC tends to really mis-train people for AC power, because AC is all about execution of work - no bench spaghetti here. And selection of approved equipment (no components from Mouser and certainly not from AliExpress!)

In particular, safety grounding is completely separate from normal current return (which is neutral), so you have to break the habit of thinking of "GND" as the current return. In fact don't even say GND in AC power lol.

Now since you installed a "GFCI outlet" I'll assume you're in North American-influenced territory and follow the Canadian or National Electrical Code (El NEC as it's called in central America).

The first area you need to focus on is called the Grounding Electrode System. That is what assures that your electrical panel box is at the same voltage as the dirt around your house. Lots of things go wrong with this in older houses - especially, the old installation relied on metal water pipe for its grounding electrode, and someone replaces a water line or meter with plastic. This has made repair of the water system in Flint, Michigan more expensive, since they are wholesale replacing old leaded lines with plastic, and then need to "open the cans of worms" that are their old electrical panels in what is often low-income tenant housing.

If your GES is not tip-top, then you will never be able to stop the panel (and all other grounded things) from being hot. So this is your first step.

Once that is done, then any grounding in your system will be at least grounded. Keep in mind NEC 2014 has new rules broadly allowing grounds to be retrofit by running appropriate sized ground wires from any junction box to the panel, another junction box that has adequate size ground (or non-flex metal conduit back to the same panel, or the bare copper wires of the Grounding Electrode System (can't be cut, you use a split-bolt connector.)

  • Thank you very much Harper, it's all worth considering! Yes I am in Canada. One thing concerning the GES; My dad a few years back routed a new cable (standard 3 wire) from the breaker panel to the garage for a dedicated outlet with a 15a breaker. This outlet had no issue whatsoever. Could it rule out a fault with it?
    – Nathan
    Nov 9, 2022 at 21:40
  • @Nathan Very old house, wiring not up to code. Will need to check how well the panel is grounded. Should have a ground wire from panel to either metal water pipe going into the ground or/and a ground wire going to one or more ground rods outside. The ground wire is for safety only in case of a fault, but sometimes wrongly use as neutral return.
    – crip659
    Nov 9, 2022 at 22:53

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