80v showing instead of 240v (UK)

[Quarky68]

Hi all - hoping you can help.

We have a three way swicth.

Switch 1 and 2 control internal lighting - all good - no problems with them whatsoever.

Switch 3 controls external lights that were fitted by a spark about a year ago. A few months ago, they started to flicker, go off until they just no longer worked. I've tested the outside junction box and lights themsleves and they are showing 80v instead of 240v. He came out yesterday, messed around and left. us being £40 lighter (excuse the pun).

They still don't work and quite frankly, I don't trust the guy anymore - £40 for not fixing it...so won't be contacting him. I fitted some outside lights last year myself and never had any issues...

I've been around the switch, lights and junction box, carefully unscrewing, checking and connecting everything back in its rightful place.

But it's still showing 80v...is the switch kaput? Or could there be another reason?

I have noticed there is no earth comeecrion to the (metal) switch plate - can't think why that would be an issue tho'?

 

[He who knows]

Lack of an earth connection won't cause the not-working problem, but it might cause danger - you should connect it.

If it all used to work then if nothing has been fiddled with, either a connection has come loose or a cable has got damaged or a light fitting has gone flaky.

Between which points are you measuring 80V, and with what?

 

[Quarky68]

Hi - thanks for the reply.

I'm measuring 80v at a junction box on the outside wall with a multimeter - negative on neutral, positive on live. Same as when I test the lights...so sounds like the wiring...

If there's a fault in the wire, it's gonna be a real pain replacing it as it's all in a void between the plasterboard and a stone wall. Not only that but it goes up and over a doorframe before hitting the switch.

Any help appreciated!

 

[AC Power]

Unplug all your accessories. If the wiring comes back a clean, then ONE-BY-ONE START RECONNECTING YOUR EXISTNG LIGHTING/STUFF BACK INTO THEIR ORIIGNAL PLACES. Take all measures (for 240) as add piece by piece.\

Thank Might Help.

 

[He who knows]

Hi - thanks for the reply.

I'm measuring 80v at a junction box on the outside wall with a multimeter - negative on neutral, positive on live. Same as when I test the lights...so sounds like the wiring...

Are you sure? With lighting circuits you cannot assume that red/black or brown/blue are L/N.

Not only that but it goes up and over a doorframe before hitting the switch.

That's wrong - not allowed a route like that for concealed cables. Not that that's the cause of the problem, but look on the bright side - if you do end up having to replace it, at least you'll be able to make it safe.

https://www.niceic.com/Niceic.com/media/Pocket-Guides/Pocket-Guide-6.pdf

You need to trace the cables, identify which conductors are neutral, which are permanent live, which are switched live, which are interconnects between 2- and 3-way switches, draw it out and then see where you should be able to measure 240V.

 

[dandlbish]

I assume you've tested the output of the switch at the switch itself. Just possible the switch has gone HR. Unlikely but it would be a great result for you, just change the 3G switch.

 

[CACJL]

Is this a fluorescent light, you would get about 80 volts across the tube, the other 160 volts is dropped by the ballast inductor.