AC circuit reverse/short


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Old 01-01-20, 09:46 AM
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Question AC circuit reverse/short

I have some odd behavior on a pair of 120V switched outlets (4 total sockets), as follows:

- Switch on (standard wall switch), sockets function normally. Outlet tester (Sperry Instruments GFI6302) shows "correct" on the plugs.
- Switch off, nothing plugged in to any socket except the outlet tester. The tester flashes very rapidly, I think between "correct" (2 yellow lights on) and "hot/grd reverse" (left yellow light on, red light on). It's hard to tell what the two states are because it flashes so fast, but the middle yellow and red are definitely both flashing.
- Switch off, something plugged into one of the 4 sockets, plus the outlet tester in another socket, the red light "pulses", again in showing "hot/grd reverse". The red light turns on, then slowly fades, and pulses on again every 3 seconds or so.
- Switch off, something plugged into any other outlet on the same home circuit (not one of the switched outlets), no change in behavior at the switched sockets.

So, clearly there is a fault, but why does it act this way? Are there obvious things I can check before having to dig into the walls to check wiring? Is there anything I can test at the breaker box?

Other things I have checked:
- I replaced the switch and the behavior didn't change. I did note that the switch is installed on the white line, where most internet diagrams show the switch being installed on the black line. I don't think that matters, but perhaps I'm totally wrong on that?
- When I shut the main circuit breaker, the circuit is off. No power anywhere. So it's not shorting with some other house circuit.
- I checked all the wiring I could, inside the sockets/switches etc, and everything looks ok. Nothing is obviously shorted, frayed that I can see.
- There are other outlets in the home on this circuit (outside of the switched outlets). I have unplugged everything from those other outlets to be sure some device isn't influencing the issue, except for a ceiling fan, which I haven't disconnected (yet). Operating the ceiling fan on/off, forward reverse, does not impact the above behavior.
- The other outlets all test "correct", but they are unswitched (always on), so the behavior is the same as the "switched on" behavior of the switched circuit. I might disconnect a power lead from one of those outlets and see if they pulse also when the circuit is open, like the above switch, which would let me know if it is the entire circuit or just the switched portion of the circuit.

Any recommendations for additional things to test that can rule out/rule in problems would be greatly appreciated.
 
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Old 01-01-20, 09:52 AM
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Welcome to the forums.

Does the circuit work normally ?
When you put a floor lamp into ANY of the receptacles... it turns on and off normally with the wall switch ?

Receptacle testers are easily fooled and don't make good troubleshooting tools.
 
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Old 01-01-20, 10:09 AM
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All receptacles function normally outside of the switched circuit. Lights etc function fine.

The switched receptacles function fine when switched on (lights work), but when off, I noticed a flashing behavior in an LED light string that was plugged into a switched receptacle, which is what made me suspicious in the first place. I thought it was the LEDs that were the problem, but a different set of LED lights as well as the receptacle tester also shows the same pulsing behavior when the switched receptacles are off. Those receptacles should not be receiving any power, but are still capable of pulsing every few seconds, so they are getting power somehow.
 
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Old 01-01-20, 10:16 AM
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Many LED products do exactly what you are experiencing. It is very possible to have the power off in a receptacle and the LED's will still flash.

Most LED bulbs now come with an added ballast resistor to help the bulb go dark.
You won't find that on light sets.

In order to fully test the circuit you would need a meter to check from hot to neutral and hot to ground. Based on your description.... the circuit is operating correctly,

If you were to plug the floor lamp in and the LED light set at the same time..... when the switch was off.... everything would be dark.
 
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Old 01-01-20, 04:54 PM
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Sounds to me like they might possibly be switching the neutral. Because if they were switching the hot, there would be no lights on your tester. Switching the neutral can create some odd symptoms.
 
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Old 01-02-20, 12:52 PM
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PJmax I haven't tested the regular light in the socket as you suggest, but the same LED string lights behave normally on another switched circuit (lit when on, no flashing when switch is off), so I think the LEDs are not to blame. When the switched receptacles are off, the receptacle tester still lights up in the strange manner described (they are not LEDs), but I think that it shouldn't light at all when the circuit is switched off.

I got a multimeter and will start testing the plugs for voltage/reversals and continuity.

joed The switch does look like it is switching the neutral. No idea why it was wired that way. Would that cause an oscillating/pulsing short as described?

I just found another switch/receptacle on the same master circuit and it seems to behave normally with the LED lights and the circuit tester.
 

Last edited by Charles1010; 01-02-20 at 12:56 PM. Reason: update
 

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