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I have a child at home who has learning difficulties. Sometimes she jumps up and down on the floor. Recently this has caused the downstairs living room light to flicker. Upstairs under the floorboards I found a connector block with the three wires from the living room light switch going in one side and obviously three wires leaving the other side. Oddly the bare earths were just twisted loosely together underneath. Now I may not be a qualified electrician, but it's obvious that twisted wires isn't what you are supposed to do, so I replaced this with a six connector block strip and connected the wires back up properly. The light then worked correctly. The other day it started flickering again and after going out shopping for a few hours I returned and the light no longer worked.

In the switch on the wall the two incoming wires are live in the off position and the single outgoing is zero volts...with the switch in the on position all wires are live. At the light itself both pins are live when switched on.

is this caused by a broken neutral or by possibly something else, if so any pointers would be helpful. All other lights work without fault and live testing was done with a screwdriver as I do not have a test meter...a bulb will light between live and earth in the circuit.

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migrated from electronics.stackexchange.com Oct 17 '12 at 2:53

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As Michael mentions, wiring diagrams and photos are helpful. See our faq if you're low on rep. –  BMitch Oct 17 '12 at 2:59
    
What does this mean, " live testing was done with a screwdriver "? –  Tester101 Oct 17 '12 at 16:46
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There are electrical testing screwdrivers with a neon light that lights up if you touch them to a live wire...hopefully he means one of those, and not "tested to see if there were sparks". –  Grant Oct 20 '12 at 0:21
    
Fixing the bare wires (ground) wouldn't have actually changed anything. It was just a happy coincidence that the problem stopped for a while. –  BlueRaja - Danny Pflughoeft Sep 4 '13 at 22:31
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3 Answers 3

Flickering is caused by a bad connection somewhere. It could be the bulb or socket that is bad (you did try a new bulb, right?), or it could be a bad connection anywhere along the line: at the fixture, switch, any electrical box along the way or a fault in a cable (staple, screw, etc.). It could be the hot or neutral that is bad. A sign of the neutral being open is other lights getting brighter or dimmer. While the ground not being well connected would not cause the flickering, it might be a sign of other bad connections along the way.

You will need to visually and physically inspect all of the connections with the power turned off. Wiggle wires, look for ones that pull out of connections. Look for nicks or otherwise degrading wires. Check the wire insulation too. Look for heavily oxidizes wires or connections.

You need to get yourself a non-contact voltage tester! You shouldn't be testing live circuits with a screw driver, that's a going to get you killed.

NC voltage tester

Call an electrician if you are unfamiliar with electrical work.

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+1 - don't test circuits with a screwdriver! Nothing good can come of that! –  Michael Kohne Oct 19 '12 at 2:46
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I don't know how much experience you have with electrical equipment but I'm sure you know that mains power can easily kill and if you don't know what you are doing, please seek professional help (from an Electrician). I would not suggest using a screwdriver for any kind of electrical testing.

In order for us to better answer your question, some pictures or illustrations would be helpful. If the problem originated from vibration then it is likely you just have a loose connection somewhere. However, when you say both pins at the light are live then it leads me to believe that the ground pin is misconnected.

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I am an electrical home inspector. In my opinion the first thing is to look for double drops in the main box. (Two wires on one breaker is a double drop). This can overload the circuit and cause flickering and a lot of other problems. If there are no double drops you need to test voltage. It may be something from the meter; if you are not getting proper voltage call the power company and have them check voltage and grounding.

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How could two wires on one breaker "overload the circuit?" And why would that cause the lights to flicker? –  BlueRaja - Danny Pflughoeft Sep 4 '13 at 22:32
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