Something going on with our hallway lights

[jayc89]

Hallway lights are on a 3 way switch - they can be turned on/off from the front door, from the bottom of the stairs and from the upstairs landing. Today we noticed that the 2x downstairs switches (front door and bottom of the stairs) weren't working, however the upstairs switch was working. Once switched on by the upstairs switched they could be turned on/off by the 2x downstairs switches. 

 

This seems to be a new occurrence. I've been drilling holes today (weather comp for boiler and to fit a new MVHR plenum) and I don't believe in coincidences, but this was at the opposite end of the house so I'd be pretty pissed if that was the case. The last time I went through a cable the entire circuit tripped, which hasn't happened with the lights, so it might not be something I've done (for a change!)

 

Any ideas what could be going on?

[Mattg4321]

Assuming it was working before, either a damaged cable or faulty switch. 

[SteamyTea]

3 minutes ago, jayc89 said:

Any ideas what could be going on?

Aliens.

[jayc89]

5 minutes ago, Mattg4321 said:

Assuming it was working before, either a damaged cable or faulty switch. 

 

We had a new consumer unit fitted last year, as part of a full re-wire, I can't remember the technical term for it, but our downstairs sockets tripped instantly when I nicked a cable previously. So I assumed the same would have happened if it was a dodgy cable. 

Would a dodgy switch cause 2x switches to act oddly?

[markc]

Loss of functionality in 2 way or 3 way circuits is usually down to a loose connection (rare a conductor just breaks) on one of the link wires. Carefully pull the switch fronts away and there is a good chance the offending wire will pull out of the loose connection

[elite]

I'd guess at wired incorrectly or a loose connection, whip the switches off (turn the circuit off first) and take some pics of what you find

[ProDave]

I would put my money on either the upstairs switch has failed, or one cable has come loose as the first place to look.  If not there, the next switch in the chain which will be an intermediate switch, that may or may not be the one at the bottom of the stairs.

[jayc89]

30 minutes ago, ProDave said:

I would put my money on either the upstairs switch has failed, or one cable has come loose as the first place to look.  If not there, the next switch in the chain which will be an intermediate switch, that may or may not be the one at the bottom of the stairs.

 

The one at the bottom of the stairs is certainly a different form to the others, the rockers are more bulky. I think the Sparky told me that was because it was the intermediate and the standard ones wouldn't fit (but it was a while ago now!) I'll take a look in the morning. 

[ProDave]

18 minutes ago, jayc89 said:

 

The one at the bottom of the stairs is certainly a different form to the others, the rockers are more bulky. I think the Sparky told me that was because it was the intermediate and the standard ones wouldn't fit (but it was a while ago now!) I'll take a look in the morning. 

Yes there are less choices of switch type for intermediate, and it is hard to get an intermediate in a 2 or 3 gang switch.

[jayc89]

Tried again this morning, flicked the upstairs switch on, downstairs lights tripped and now that rocker is jammed on, meaning we have no downstairs lights at all. I'm guessing that's the problematic switch!

[markc]

21 minutes ago, jayc89 said:

Tried again this morning, flicked the upstairs switch on, downstairs lights tripped and now that rocker is jammed on, meaning we have no downstairs lights at all. I'm guessing that's the problematic switch!

Yup! So much easier when things fail mechanically

[jayc89]

Any idea what make these are?

 

 

Looks like they could be BG - https://www.toolstation.com/bg-polished-chrome-10a-switch/p10148?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=_dc&pcrid=&pkw=&pmt=&gclid=Cj0KCQiAorKfBhC0ARIsAHDzsltijLHa5U6HK3OkOpz9a8rtPdRr7iHItDcX4MVN5wZQCAnL7xPRsfAaAqZVEALw_wcB&gclsrc=aw.ds

 

Which would make sense as our sockets match the BGs too (polished chrome with grey pin surrounds)

[Mattg4321]

Looks like BG, although a failed switch doesn’t usually cause MCB/RCD to operate. Points more towards damaged cable or perhaps even pinched cable behind switch. 
 

You need to turn the power off and unscrew the switches to start with. Make sure all lighting circuits are off - there may be more than one in a 2 or 3 gang switch. 

[jayc89]

Managed to sort it. Replaced with a new double switch and all seems well again!

[ProDave]

5 minutes ago, jayc89 said:

Managed to sort it. Replaced with a new double switch and all seems well again!

If the MCB tripped earlier and a switch welded, that is a short circuit somewhere.

 

Most likely explanation is a pinched cable in the back box of the switch you have just replaced, and in the act of replacing the switch it is no longer pinched and causing a short circuit.  Prime candidates are too tight behind the switch in a shallow back box, or one of the fixing screws pinching a cable.