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I am working in my unfinished, detached garage (North American wiring). It has two 110/120 volts, neutral, and ground coming into a mains breaker and then to breaker box for the garage.

I have two sets of ceiling lights, each set has two sockets for standard bulbs. I wanted to, and have removed the wiring from between the breaker box and one set, and had planned to join that set to the first set so I had 4 light sockets on a single breaker. The breaker is 20 amp and is currently connected with armored and rubber sheathed wire. I think 12/3 or 14/3 but only one of the hot wires is actually hot and the other one you can see, for all circuits is cut and coiled inside the breaker box when you take the breaker box panel off.

The problem I am having is that right now I have one set of lights, two ceiling sockets that are connected to each other. They are not connected to any circuit anymore or anything else. My chirper (non-contact voltage tester) is giving me chirping / lighting on the ground wire. This wire only connects two disconnected lights. I am getting the same alerts on rubber coated armored sheath of the 12/3 / 14/3. I am also getting this on the studded metal plates that connect the wood joists. Ironically I'm getting this from wood itself. This aside from the armored wire, this seems contained to a 4'x 4' area of the ceiling joists. It also seems to be inconsistent in that sometimes it lights constantly but sometimes it doesn't.

I can't find the cause of this problem and I am concerned to work on these wires or outlets now. I have tried turning off different circuit breakers to find the cause but it seems like it's not any one circuit and circuits that are nowhere near that area still trigger it.

To sum this up, I have two light sockets that disconnected from everything but each other so there is no current and I am getting alerts on the ground, the junction box, the armored wire interconnecting them, the studded metal plates holding wood joists together and the from wood itself and I can't find the cause.

I have traced and tested everything in that area. I would bet there is no mystery wire I have missed and it's an unfinished ceiling so it's very easy to see all wires. I'm stumped.

Looking forward to replies.

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    Some of these non-contact detectors respond to induced voltages. I have heard that if the battery is low, then these detector respond more to induced voltages. – Jim Stewart Nov 10 '17 at 22:25
  • I'm reading about induced "ghost" currents now. How do I test against a metal junction box our ground wire. I mean, to the best of my knowledge I don't have a complete circuit. To the best of my knowledge none of these wires or any part are connected to anything. It's like each light socket are opposite ends of an extension cord that's detached. Anyways, my point is, how do I verify that this is induced? – jetole Nov 10 '17 at 23:30
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    Your subpanel in the garage. Does it have its neutral and ground bus separated? Is there a separate neutral and ground wire coming over from the house? – Harper - Reinstate Monica Nov 11 '17 at 0:34
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    De-energizing the garage for service is easy, go to the main panel and shut off power to the subpanel there. – Harper - Reinstate Monica Nov 11 '17 at 0:37
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Well here is some background that may assist. Trouble-shooting electrical faults in house hold wiring is something that requires skill. Even a one and two year apprentice may have difficulty finding and correcting this issue. Trying to do it through correspondence in near impossible. In the following are some testers I might recommend. These are available at the box stores and ebay/amazon, etc.
Klein #ET250; Sperry #61000; Extech #VT10. These will do a good job testing for voltage and continuity. And they are handy to use for this type of work. These things are not cheap. You may consider using this money to defray the cost of a pro. Good Luck. P.

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A non-contact tester is wholly inadequate as a stand alone test instrument. In the right and skilled hands it can be of assistance and reduce the overall trouble shoot time. In an amateur's hands it is useless. For an amateur it can tell you if voltage is present in a lamp cord of hot side of a receptacle, very little more. It was never designed to do more. A genuine VOA meter is a minimum to look for faulty wiring problems. Big Box stores is a good place to get one. P.

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  • I appreciate the insight but can you elaborate in that you haven't explained what to test or how. I am looking at VOA meters now but... then what? BTW are you talking about a analog VOA meter? When someone says VOA do they typically mean the analog ones like is that the norm when you say VOA meter? Looking forward to your reply. – jetole Nov 11 '17 at 14:21
  • @jetole an analog meter is a good meter - digital meters can detect phantom voltage and leave 'doubts' . Analog meters will read the voltage - but the old school needle bothers some people - so they pick a dmm with a LoZ function (low impedance function). LoZ helps troubleshoot things where phantom voltage or bleed voltage exists - such as in Thyristors . – Ken Nov 12 '17 at 22:49

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