Help with 70s house light switch wiring?

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bit

19 posts

Geek

#289646 19-Sep-2021 20:00

I'm replacing both light fittings and switches in my house currently, replacing with LED lights and smart switches.

Some switches have been straightforward (those which connect to pendant light fittings), but there have been some where I'm running into something odd (those connecting to downlights).

Here you can see the back of the switch - this goes to a single light fitting. I have

C = Common/Phase = straightforward.

Wire nut = Neutral = straightforward.

Yellow wire???? Ordinarily I'd say yellow is for Earth. But would it be just a badly chosen colour and it's actually the live feed for the bulb?

Looking at the fitting for the bulb is no help - it has black / red / yellow all connected to where you would expect - ie neutral, phase and earth on the fitting.

I am tempted to get up in the roof and do some actual tracing, but between the batts and the central heating ducting it's not much fun. Hopefully someone can help out here and save me a mission!

Thanks

rcooke

8 posts

Wannabe Geek

#2780790 19-Sep-2021 20:15

Not sure why it's yellow, but you may have 2-wire (no earth) light wiring there. Friends of ours had the same 2-wire lighting and they had to get a sparky to run new (current code) wiring. I'm sure others will confirm / deny though.

bit

19 posts

Geek

#2780795 19-Sep-2021 20:31

Thanks, as alluded to, it's not the only switch like this. There are quite a few.

This is another one i've removed - seems to have green pen / marker /dye on the 1 terminal. This is a PDL brand (don't think the green would be factory?)

It was wired the same - red in the C terminal, black in the loop, and yellow (with green stripe) in the '1'

pipe60

127 posts

Master Geek

#2780801 19-Sep-2021 21:10

The Green stuff you are seeing is the plasterciser coming out of the cable, There will be a J box in the roof where the yellow will conect to the red going to light, just swap it the switch like for like, could consider changing the cables that are leaking

sparkz25

750 posts

Ultimate Geek
Inactive user

#2780819 19-Sep-2021 22:05

As @pipe60 mentions, that green stuff is from the cable, make sure you wash your hands after touching that and dont get it in your eyes, it will hurt!

Take a look in the ceiling, there is probably a Jbox in there for that switch as @pipe60 also mentions, at some stage in the life of the house it has been rewired or had those downlights installed.

Also we don't use wire nuts here in NZ only in america.

SomeoneSomewhere

1802 posts

Uber Geek

Lifetime subscriber

#2780823 19-Sep-2021 22:15

Prior to around 2000, the standard phase colours were red, yellow, blue. They changed yellow to white in newer installs when they started using green/yellow instead of plain green for earth.

As above, that cable probably goes to a junction box that was added when the downlights were installed, as it was probably surface battens before that. I would probably want to check that it's in a proper junction box and not just hanging in space.

The green goo comes out of very early TPS cable - it reacted with the copper over the years. It's not a major danger but be careful with the cable - the insulation will be more brittle and might crack. If it cracks you should replace the cable.

bit

19 posts

Geek

#2780825 19-Sep-2021 22:20

Thank you very much to all who have replied.

Just one other quick question - on the 'wire nut' - have I just used the wrong term, or is the orange thing in the very first image (with the neutrals in it) not supposed to be there?

SomeoneSomewhere

1802 posts

Uber Geek

Lifetime subscriber

#2780827 19-Sep-2021 22:23

Screw terminal or loop terminal, or a few other names.

The US equivalent is a wire nut, but they twist on rather than you inserting the wires and screwing them down.

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snnet

1410 posts

Uber Geek

#2780877 20-Sep-2021 09:05

Be very careful with the green stuff, use gloves as some of the older stuff can be very harmful and contain PCB pollutant!

richms

28168 posts

Uber Geek

Trusted

Lifetime subscriber

#2780902 20-Sep-2021 09:50

Is there a second switch for these lights anywhere? for a while red/yellow/blue cable was used for 2 way switching, before it changed to white, but after they actually prohibited re-identifying the green earth as a second phase cable (Or worse, just using it as is with no sleeving) Usually there would be a blue as well, but sometimes there would be 2 wires from the main switch to the second one and then a single wire from there up to the light. The cable in that downlight looks newer so there will be a join somewhere that should clear things up.

Richard rich.ms

snnet

1410 posts

Uber Geek

#2780922 20-Sep-2021 10:44

richms:

Is there a second switch for these lights anywhere? for a while red/yellow/blue cable was used for 2 way switching, before it changed to white, but after they actually prohibited re-identifying the green earth as a second phase cable (Or worse, just using it as is with no sleeving) Usually there would be a blue as well, but sometimes there would be 2 wires from the main switch to the second one and then a single wire from there up to the light. The cable in that downlight looks newer so there will be a join somewhere that should clear things up.

This one, going by the first photo, will be an odd rendition of a three plated switch of sorts, there's nothing in the 2 way terminal of the switch so as mentioned above I'd say it's joined in the ceiling to a different cable