Mains socket neon switches are dim and the socket does not supply current

[nowthendiy]

I have a twin mains socket with two neon power switches. When I toggle a switch to the ON position, it is much dimmer than it should be. Also, when I plug a device into the mains socket, the device will not work. I assume this is because no current is being supplied. If I meter between Live and Earth (when no device is plugged in), I measure 240V. (BTW, the socket is a spur.)

Can anyone suggest what might be the likely fault.
Thank you

 

[FrodoOne]

If you are using a High Impedance digital meter (as I suspect you are), your 240 V reading may be what is termed a "Phantom Voltage" and the Line or Neutral has actually become disconnected, at the outlet or at the previous connection point..
If it is a Fused Spur, the fuse may have blown.

Plug in an appliance to one Socket-Outlet (to "load" the circuit) and take Line-Neutral, Line-Earth and Neutral-Earth readings at the other.

 

[JohnD]

Quite likely a loose connection in a terminal.

 

[nowthendiy]

The terminals in the back of the socket are fine. I suppose there could be a problem within the socket itself innards. Other than that, I suppose that I will have to do the unenviable task of crawling under the floor to find out what is upstream of the spur, unless anyone has any clever ways of locating the resistance in the circuit.

 

[JohnD]

If the person who fitted it had any sense, he will have spurred from the nearest convenient socket.

 

[FrodoOne]

The terminals in the back of the socket are fine. I suppose there could be a problem within the socket itself innards. Other than that, I suppose that I will have to do the unenviable task of crawling under the floor to find out what is upstream of the spur, unless anyone has any clever ways of locating the resistance in the circuit.

With an "appliance" plugged into one Socket-Outlet (to "load" the circuit), what voltages do you read from
Line to Neutral, Line to Earth and Neutral to Earth at both
the rear terminals and
the vacant Socket-Outlet?

 

[nowthendiy]

FrodoOne, here are my readings:

Measurements at front of socket with NO appliance plugged in and the switch on:
L-E: 236V
N-E: 122V
L-N: 15V but fluctuating

Measurements at front of socket with appliance plugged in and the switch on:
L-E: 235V
N-E: 234V
L-N: 0V to 15V but fluctuating

Measurements at rear terminals with NO appliance plugged in and the switch on:
L-E: 235V
N-E: 123V
L-N: 18V but fluctuating

Measurements at rear terminals with appliance plugged in and the switch on:
L-E: 236V
N-E: 235V
L-N: 0V but fluctuating

Measurements at rear terminals with NO appliance plugged in and the switch off:
L-E: 236V
N-E: 0V
L-N: 0V

So, my voltages are as I would expect them to be at the rear terminals with NO appliance and the switch turned off. It is only once the switch is turned on that a voltage appears on the Neutral line, even without a load.

 

[SUNRAY]

Your neutral is missing.

I assume there is only one cable (Three wires) feeding this socket.

Do you have any idea where the cable runs from ( a nearby socket etc) ?

 

[nowthendiy]

Thanks for replying so quickly. Yes, there is only one cable. It is not clear where this socket is spurring from. It sounds like I will have to get under the floorboards. Would you be kind enough to explain how you worked out that the neutral is missing?
Thanks

 

[nowthendiy]

Is the Neutral line actually connected to Earth somewhere by the consumer unit? So, presumably, the fact that the neutral is not remaining at 0V would tell you that it is not connected. Do you understand why the neutral is 122V when the switch is turned on? and 240V with an appliance connected?

 

[SUNRAY]

There should always be 235V between L & N (red & black or brown & blue) and between L & E
There should be no more than a volt or two between N & E

 

[SUNRAY]

Is the Neutral line actually connected to Earth somewhere by the consumer unit? So, presumably, the fact that the neutral is not remaining at 0V would tell you that it is not connected. Do you understand why the neutral is 122V when the switch is turned on? and 240V with an appliance connected?

N & E will generally be connected together at some point but possibly not in your property.

Half voltage? yes basically it is down to leakage which is perfectly normal in AC circuits, in this instance it is possibly showing because of the neon and the very high impedance of your electronic meter. All very acceptable.

Have you checked the wires are terminated correctly, actually checking the screw/clamp is against the copper and not the plastic insulation?

EDIT: I've just gone back to your original post and se you state it is a spur, does this mean you know where it is spurred from and does that socket work ok?

 

[RandomGrinch]

Do you understand why the neutral is 122V when the switch is turned on?

Probably due to the neon dropping some of the voltage?

---aah, beaten to it!

 

[nowthendiy]

Well. Thank you very much for your explanations and your diagnosis. I have just taken up the boards and discovered that the spur is at least 15 feet away from the socket from which it is spurring. However, there was a junction box very close to the spur. I discovered that the neutral wire was broken as you predicted. So, we are all back up and running. Many, many thanks to you for all your help. I remember my Dad telling me that a screw connection is always just about to come loose. Unfortunately he is isn't around any more to tell me how his ring main evolved. But it's all done and dusted and my mother is a happy camper. Is there a better way to connect cables than using a junction box with two wires trapped under the one screw? If so, I would gladly replace it with something more reliable.

 

[flameport]

something more reliable.

Ashley J803 Maintenance Free Junction Box 32A 3 Terminal | Hager (J803)