Tracing / fixing a damaged spur

[Sarrusophone]

Hello,

We live in a late-90s townhouse. One of the bedrooms on the top floor has 3 sockets. One of them has never worked. This never bothered us before because it was behind some immovable wardrobes but we’ve now got rid of them and I would like to put it into service.

This socket is a spur and must be a later addition to the house since the cable has blue, brown + earth rather than the old style red & black which are used elsewhere. The fault has always been on the neutral: live and earth both seem ok. I presume this means one of two things: the cable is damaged in a way which has broken the neutral but not the other two, or there is a problem with the neutral connection where it is spured off the ring?

The problem I have is that I cannot find where the cable connects to the ring: the other sockets in the room only have two cables going to them and not three. The next room along is a bathroom with no obvious mains connection. I’ve also checked the closest socket in the room beyond that but again that is just a two-cable ring.

Visually, removing the back box doesn’t give me much of a clue since that wall has sound insulation and so I can just see a mass of Rockwool and a wire poking through. I should say that the installation of that was’t the problem: the socket wasn’t working before that happened (although it clearly would have been sensible to have taken that opportunity to sort it out!)

Could anyone give me some tips as to the best way to trace a cable in these circumstances? I can see some cable tracers are available and wouldn’t mind spending some money on one as long (as it doesn’t cost more than getting someone in who owns one!) but the range of prices is huge and I am not sure if a £20 or £50 would do it.

I’ve also wondered if the cable was spurred in the loft (since that’s immediately above this room) and the spur then dropped down to the socket? Would that be a normal way of doing things? I am not sure if it is usual for there to be ring cables up there and I thought I would ask here first because access is a bit difficult. Other than that, I guess it would be under the floor which will make it almost impossible to find without a lot of work?

Thanks very much as always,

Jacob

 

[Taylortwocities]

Blast from the past
[GALLERY=media, 690][/GALLERY]
Could be anywhere. Often a junction box under the floor.

 

[markyd1]

Do the cables come into the top of the back box or the bottom....that will give you a clue where to start looking, also are there any screws in the wall vertically or horizontally from the faceplate

 

[Sarrusophone]

Blast from the past
[GALLERY=media, 690][/GALLERY]
Could be anywhere. Often a junction box under the floor.

That’s exactly the chap I need. Do you know his number? The crystal ball looks a bit complex for DIY

Do the cables come into the top of the back box or the bottom....that will give you a clue where to start looking, also are there any screws in the wall vertically or horizontally from the faceplate

It’s a bit more complex than that, unfortunately. When they did the soundproofing they brought the wall forward slightly so nothing is as it was before the words were done. I guess I need to do some digging in the Rockwall for clues as to which way it goes.

 

[JohnW2]

.... The fault has always been on the neutral: live and earth both seem ok. ....

How have you determined that?

Kind Regards, John

 

[dannyboi2003]

You mentioned the wall has been soundproofed, was that done whilst you owned the property or before? I'm thinking the socket position could be original to the house and when they soundproofed the wall the cables were not long enough to reach so they've used a junction box to extend to the new position, that's probably where the issue is.

 

[Sarrusophone]

How have you determined that?

Kind Regards, John

When we moved in we borrowed one of those plug-in mains socket testers. It came up with “neutral fault”. I’ve also checked it with a multimeter which gives me mains voltage between live and ground but nothing between live and neutral. I assumed that meant a fault with the neutral but perhaps it is indicative of another problem?

You mentioned the wall has been soundproofed, was that done whilst you owned the property or before? I'm thinking the socket position could be original to the house and when they soundproofed the wall the cables were not long enough to reach so they've used a junction box to extend to the new position, that's probably where the issue is.

The soundproofing was when we owned the property and after the fault existed, so we can’t blame them. They did extend the cable for the reasons you identified, simply by adding another 4 inches or so on with a connector strip. I’ve checked the continuity and that is fine so it isn’t an issue. Also, the cable before the connector strips is blue / brown which means it must be a later addition to the house since the original wiring was all red / black. (And, because it was a 1990s build, they assumed that we only needed 2 sockets in each room!!)

 

[JohnW2]

When we moved in we borrowed one of those plug-in mains socket testers. It came up with “neutral fault”. I’ve also checked it with a multimeter which gives me mains voltage between live and ground but nothing between live and neutral. I assumed that meant a fault with the neutral but perhaps it is indicative of another problem?

Thanks for clarifying. You seem to have drawn the correct conclusion from what the tests have shown. For completeness, did you (with your multimeter) measure between neutral and earth?

Kind Regards, John

 

[Sarrusophone]

Thanks for clarifying. You seem to have drawn the correct conclusion from what the tests have done. For completeness, did you (with your multimeter) measure between neutral and earth?

Kind Regards, John

Nothing, I’m afraid. I’m not sure if I should expect to get something, even if everything was working? I thought that was about all the testing I could do from one end of the cable without finding where it is wired up...

 

[dannyboi2003]

Damn was hoping that would be the issue for you with an easy fix. As someone's already said it's probably fed from a junction box under the floor, is lifting the floor an option for you to investigate? I hope the enclosed the connector blocks they added in a box or something and not just stuffed them in the wall!

 

[JohnW2]

Nothing, I’m afraid. I’m not sure if I should expect to get something, even if everything was working? ...

If everything were working, there might be a small voltage between neutral and earth, but not much.

However, one way you could get 'mains voltage' between L and E, but not between L and N is if (for whatever reason) the N was also at 'mains voltage' relative to earth - in which case you would see 'mains voltage' between N and E, That would be very unlikely but, since not totally impossible, is why I asked!

Kind Regards, John

 

[Sarrusophone]

Damn was hoping that would be the issue for you with an easy fix. As someone's already said it's probably fed from a junction box under the floor, is lifting the floor an option for you to investigate?

Well...It is an option. Not the most attractive one for obvious reasons! I’m also wondering where to look because starting from where the broken socket is, is the least convenient place to lift the floor (inevitably). I’ve drawn a quick sketch. I don’t suppose there is any usual practice which might make it easier (e.g. I’m wondering if it would be near one of the existing sockets)? I appreciate that is probably wishful thinking...

I hope the enclosed the connector blocks they added in a box or something and not just stuffed them in the wall!

Of course it isn’t! And I certainly wouldn’t have realised that that is what had been done had I not been poking around into the rockwell to see if I could find where this cable was going...

If everything were working, there might be a small voltage between neutral and earth, but not much.

However, one way you could get 'mains voltage' between L and E, but not between L and N is if (for whatever reason) the N was also at 'mains voltage' relative to earth - in which case you would see 'mains voltage' between N and E, That would be very unlikely but, since not totally impossible, is why I asked!

Kind Regards, John

Ah. Yes: I can see that. Thank you.

 

[Sarrusophone]

PS. Might I just double-check a question from my initial post? Would any of the cable finders that you can buy help with locating the junction box?

 

[JohnW2]

PS. Might I just double-check a question from my initial post? Would any of the cable finders that you can buy help with locating the junction box?

I personally very much doubt it.

Kind Regards, John

 

[JohnW2]

Another thought - are we even sure that the socket in question is on the same circuit as the other two sockets in the room?

If you know, or can determine, which MCB or fuse in your CU is supplying the other two sockets, you could 'switch that off' and then use your socket tester or multimeter to determine whether there was still 'mains voltage' between L and E at the problem socket.

Kind Regards, John