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  1. #1
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    Default Dim open neutral reading on 3 light testor on half hot

    I get a dim light on the 3 light tester (the right hand light indicating open ground) on a half hot socket with the switch turned off . There are four half hots in the home and two have this while the other two do not; any thoughts as to why. Thanks

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  2. #2
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    Feb 2009
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    Default Re: Dim open neutral reading on 3 light testor on half hot

    It may be stray voltage leaking across from the hot terminal. A cheapo 3 light tester can't be trusted for anything more than basic on or off testing, and even then can give false readings.

    If there are no obvious wiring faults or loose connections, confirm by testing with a DMM or a higher quality tester.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  3. #3
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    Aug 2011
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    Bennett (Denver metro), Colorado
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    Default Re: Dim open neutral reading on 3 light testor on half hot

    I see this several times a year. If I find it on one switched outlet in the house, odds are that all will have it. An electrician buddy told me that it rarely is a safety issue. The bleed across voltage is usually too low to be a problem, BUT it's still wrong and shouldn't happen. He told me that he thinks it's a manufacturing defect in the switches or outlets. That may explain why I often see it in all the switched outlets in a house. The builder bought all the switches and outlets at the same time from the same lot.

    I write it up and plan on doing some explaining when I do.

    If you choose not to decide, you still have made a choice.

  4. #4
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    Mar 2007
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    26,252

    Default Re: Dim open neutral reading on 3 light testor on half hot

    That is when you put the cheap 3-light tester down and use it what it is good for - a night light.

    Then you take out your multi-meter or similar voltage tester and actually test the voltage at the receptacle, checking hot-neutral, hot-ground, and neutral-ground checking for the proper voltage readings.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  5. #5
    Join Date
    May 2009
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    Washington State
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    358

    Default Re: Dim open neutral reading on 3 light testor on half hot

    Quote Originally Posted by mark petty View Post
    I get a dim light on the 3 light tester (the right hand light indicating open ground) on a half hot socket with the switch turned off . There are four half hots in the home and two have this while the other two do not; any thoughts as to why. Thanks
    I carry two different brands of outlet testers in my bag just so I know it's not the tester. If they both have the "dim" light and it's flickering, it's the house, not the tester. More often than not, some weekend warrior has taped a ground wire to a rusty / corroded / painted water pipe, trying to ground 3-prong outlets, usually in a Pre-'62 house - have seen it several times.......

    Jerry's way is the best, hands down, but, it is time consuming for those of us that test each and every outlet trying to find which one was done after a "liquid-lunch" on a Friday. The two-brand outlet tester method works great, never had an issue or a callback.....

    Last edited by Jim Hintz; 04-08-2013 at 09:31 PM.

  6. #6
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    Mar 2009
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    601

    Default Re: Dim open neutral reading on 3 light testor on half hot

    There are a number or reasons this happens, but illuminated switches and dimmers are among the culprits I find most often.

    You are MUCH better served testing things with an analog meter and a an appliance lamp of 7.5 watts or so mounted in a lamp socket that plugs in. There are permitted amounts of current leakage in some types of devices and the neon lights in the tester light with very little current - normally not enough to gate the solid state electronics in a dimmer which the lamp would accomplish.

    You can light the lamp (or several) in a neon tester by holding one lead and applying the other to a hot wire - though I don't recommend it. The method is often used by old school electricians to find the hot wire in old circuits where the colors are gone and everything looks the same.

    Any way, in short, you'd really be better off without the 3 light tester.........

    Occam's eraser: The philosophical principle that even the simplest solution is bound to have something wrong with it.

  7. #7
    Join Date
    Aug 2011
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    Bennett (Denver metro), Colorado
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    Default Re: Dim open neutral reading on 3 light testor on half hot

    Quote Originally Posted by Bill Kriegh View Post
    There are a number or reasons this happens, but illuminated switches and dimmers are among the culprits I find most often.

    You are MUCH better served testing things with an analog meter and a an appliance lamp of 7.5 watts or so mounted in a lamp socket that plugs in. There are permitted amounts of current leakage in some types of devices and the neon lights in the tester light with very little current - normally not enough to gate the solid state electronics in a dimmer which the lamp would accomplish.

    Any way, in short, you'd really be better off without the 3 light tester.........
    I see it usually on regular toggle switches and usually on homes built between the mid 80's to the late 90's. I don't see how an analog meter or an appliance lamp is going to change the basic assessment learned from the 3-light tester that we have some current "bleeding" or "leaking" across the switch/outlet.

    If you choose not to decide, you still have made a choice.

  8. #8
    Join Date
    Mar 2009
    Location
    Colorado Front Range
    Posts
    601

    Default Re: Dim open neutral reading on 3 light testor on half hot

    Current leaking across some devices switch isn't necessarily a problem. Many devices need a solid connection, like a ballast or the filament of a lamp to function correctly - that is, the electronics can't/won't completely shut off the output without a complete circuit. A neon light usually doesn't have a connection other than a very high resistance and ionized gas to make the circuit. Consequently, a neon light won't necessarily tell you the device under test is working right. Further, it takes so little current to operate one that induced currents in a wire that is not energized can light one.

    If in fact you are testing a circuit with a standard switch turned off and getting an analog meter needle to swing and show voltage there is a problem. A neon light doesn't tell you anything, and certainly not that there really is leakage across a switch. In a split receptacle circuit a 3 wire cable is used, and the newer cables have a thinner insulation than the old ones, putting the switched conductor closer to the hot wire than with older cables. The difference can be enough that the induced current lights the neon light.

    I expect this problem to get a bit worse because they have started making 3 and 4 conductor cables with no conductor twisting. The twisting helps mitigate induced currents, though that's not the reason the cables were twisted

    Occam's eraser: The philosophical principle that even the simplest solution is bound to have something wrong with it.

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