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I was troubleshooting a home circuit that appears to have 4 double receptacles and one light on it. One of the receptacles works fine as does the light. The other three show 120 vac hot to neutral and hot to ground. Neutral to ground shows 0 ohms. I'm told the three problem receptacles worked for years and then just stopped. I plugged an answereing machine with an led call count indicator into one of the bad receptacles. It would not fully light up but it was barely illuminating in a pulsing fashion at I would guess 2 or 3 cycles/second. I plugged a cell phone charger into it. It would pulse charging/ not charging at about the same rate. The multimeter showed a solid 120 vac. I tried an incandescent light, but it would not illuminate. I did not check the neutral connection at the load center since one receptacle and the light worked fine. I was told there are no GFI's in this circuit despite one receptacle near the kitchen sink (but it is an old house). Any ideas what is causing this?

  • Is the lamp a dimmer? Did the other outlets fail when it was upgraded? – Harper Feb 11 '18 at 23:25
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My guess is that some part of the wiring chain from outlet to outlet is using back stab wiring connections at the outlet. These can develop intermittent faults that will pop in and out of connection depending on how much current is being asked for by the load. In the case of your multimeter it represents almost no load on the circuit and the intermittent connection stays connected and permits the AC voltage to be read. Light loads cause the on/off behavior that you are seeing. A heavier load results in the intermittent opening up until the load is removed.

You will want to inspect the outlets to see if there are indeed back stab wire connections. If so remove them and replace with new quality outlets that use screw terminals or screw clamp connections for the wire.

As always advised when working with electrical fixtures turn off the circuit at the breaker panel (or fuse box if it is really really old). If you are unsure of working with electrical or not at all familiar with it then call in a licensed professional electrician.

Also keep in mind that intermittent electrical connections can be very dangerous and create heat and cause fires so address this problem as soon as possible. Be advised it may be in your best interest to shut off this particular circuit at the panel until it can be properly repaired.

  • Thank you Michael. They are old non-stab receptacles, but I will check all screw connections. It appears more than one person has messed with them over the years. I found the second to the last in the chain had wire extensions added that were twisted poorly soldered and taped. I thought for sure that was going to be the problem, but it wasn't. – Bob G Feb 11 '18 at 23:18
  • @BobG Don't just focus on the out ones. Also focus on the last working one in the chain. – Harper Feb 11 '18 at 23:27
  • Soldered? You are in America? This is unusual. Oh, btw - is any of the wiring aluminum? To @MichaelKaras's point, its very likely there is bad connections in the circuit. See if you can isolate the upstream connection in the path and consider replacing that connection. Be it a light, a switch, a wirenut, an outlet, etc. By code - any boxes should be accessible, butits possible one isnt. Be careful. – noybman Feb 11 '18 at 23:27
  • Soldered is legal, but must be taped well which is a lost art. I have dismantled wiring on historic equipment and taping is really quite intricate. I can live with soldered extensions (not sure if Code can) but I would use shrink tubing to insulate them. – Harper Feb 11 '18 at 23:35
  • The soldering was terrible but the taping was pretty good (great considering it was deep in the wall). I pulled it apart and replaced with wire nuts. – Bob G Feb 12 '18 at 1:16

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