replaced light switch - 2 way switch develops intermittent issue after a week

[MrDerek]

Hi, hope you lovely people could help, I couldn't find anyone with a similar issue and not able to get any professionals out this close to Christmas, will try and keep it short and to the point.

Upstairs light controlled by 2 switches at top and bottom of stairs.

Downstairs switch I had to replace, tried to follow the old wiring but it fails very intermittently after a week; when turning on from the new switch it would come on briefly before quickly going off. When this happens the upstairs switch will not work for a few flicks of the switch or until I turn the downstairs switch off. This would happen about 5% of the time and only happens with the new downstairs switch. It's a 3 gang switch, the other 2 seems to be fine. The fault developed after a week of replacing the switch, at first I thought I had a loose wire so opened it up to tighten everything and it seemed to have resolved the issue, but issue came back after another week.

Not touched upstairs switch at all.

Old wiring (left switch) (L - yellow, L1 - blue, L2 - red)

New wiring (left switch) (COM - yellow, L1 - blue, L2 - red)

Reading other peoples post most seem to have swapped a wire, but looking at my images it doesn't seem like the case here. Faulty switch?

Clutching at straws, I've replaced a metal switch for a plastic one, new plastic switch didn't have anywhere for the earth wires so I wired them all into the back box, which I believe is the correct thing to do?

Appreciate all replies
Derek

 

[terryplumb]

If it worked initially ,and now sometimes doesn't work ,it sounds like a faulty switch ,or loose connection.

 

[SUNRAY]

Well done for taking the before photo. We wish everybody did that.

It all looks good and I assume you haven't mixed up any reds or yellows.

I suggest temporarily swapping 2 switches over, ie making the right switch the 2 way and see if the fault moves.

 

[conny]

Possibility of insulation trapped under a screw but occasionally allowing a circuit?

 

[MrDerek]

Well done for taking the before photo. We wish everybody did that.

As someone who doesn't really know what they're doing most of the time I make a habit of taking photos of everything

It all looks good and I assume you haven't mixed up any reds or yellows.

I suggest temporarily swapping 2 switches over, ie making the right switch the 2 way and see if the fault moves.

Starting to doubt myself, but if I had mixed up the reds and yellows from other switches would the other switches work as expected? we've not seen any issues with the other 2, although they don't get as much use.

Possibility of insulation trapped under a screw but occasionally allowing a circuit?

Interesting thought, will check them out, thanks

 

[MrDerek]

Just to update in case it helps anyone, when I made this thread I got behind to take pictures and triple check wiring, while I did that I tightened absolutely everything again.

Issue has not come back in 2 months, must've just been a loose wire or as Conny had said might have been insulation. If it ever does come back will assume it's a faulty switch and try a new one.

Thanks again to everyone who offered advice.