50-70v between L-N on a ring?

[HappyHippyDad]

A customer asked me to replace 2 sockets in her house as she said they had stopped working. When I tested both sockets one was a spur and the other a spur off that spur. They both had 240v L-E and 50-70v L-N. The MFT tester showed 70v and the fluke showed 50v. I wish I'd put the Drummond on to see if it was ghost voltage!

She states they were working fine but then didn't. She was pretty vague about when this happened, but I think it was recent. She was pretty vague about everything really, but She states she plugged a lamp into one of them and the lamp blew. She has had plasterers in and also an electrician recently.

My thoughts are perhaps a screw through the neutral somewhere? Or perhaps the neutral has just been disconnected in the socket supplying the spur?
Any other thoughts?

Cheers all.

 

[ipf]

If she wants a repair, isolate, disconnect at the point of the initial spur and begin your dead testing.....if they are the only sockets affected.

 

[Andy78]

Failed connection at the point where the spur is taken from the ring would be my first look, if the ring itself has normal voltages.

EDIT: Beaten to it ^

 

[Octopus]

Do an Rn + R2 ..... Then a R1 + R2

And compare

 

[Octopus]

Do an Rn + R2 ..... Then a R1 + R2

And compare

 

[Octopus]

That's odd I only hit the post button once!

 

[dmxtothemax]

The voltage readings in the initial post would indicate a poor neutral,
That's where I would start.

 

[Richard Burns]

With 240V line to earth you can perhaps assume line and earth are normal.
Therefore testing line to neutral and getting 70V indicates that the neutral is at 170V to generate that potential difference, testing neutral to earth would probably have shown this 170V.
The neutral should be securely connected to 0V and this is not the case therefore the neutral has a resistance somewhere i.e the neutral is nearly (completely if it is a floating voltage measured and sicne you got 50-70V it sounds likely) disconnected.

Since the customer has had a lamp blow this could generate a high current peak as the filament separating sustains a fault arc briefly. This high current could apply an electromagnetic force to the circuit live conductors and if any were loose they could become disconnected. Find the point of supply for these sockets (install a fused spur so there is not a spur on a spur!) and rejoin the neutral.

Hang on, this was what you said in your opening post!

 

[HappyHippyDad]

Many thanks all.

I shall be going back to the customer at some point and shall try and remember to update!