2 Gang Light Switch - One Now Operates Wrong Circuit

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RealPolitik

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A few months ago I replaced a broken 2 gang 2 way switch - one gang operates an internal fluorescent tube, the other a pair of PIR halogen floodlights. I wired it exactly as the original switch. The floodlights (also new replacements) are wired as originally so that either PIR sensor turns them both on; in one position the switch leaves them controlled by the PIR sensors, the other way they’re permanently on.

This was all working fine until this week, when it seems that the floodlights have been staying on permanently. Now, the PIR sensors are not triggering the floodlights, and when the turned on manually, the floodlights can only be turned off by the switch which controls the fluorescent tube (which also turns off the fluorescent tube).

Any ideas what might have gone wrong?
 
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The only thing that could have changed is that the PIR has failed.
The other things are not really possible if working correctly after your switch replacement.

Picture showing all the wires at the switch and to which terminals they are connected.
 
Thanks, that’s what I can’t work out - will take a photo in the daylight.
 
This is the before: 4352602D-2BE3-4062-8740-2C7FC184ACC8.jpeg
 
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I take it that the fluorescent tube can also be operated from another switch.

I can see an error so I think it must always have been the same - apart from the PIR not working.


All red wires makes it difficult. Did you mark them by any chance?
 
No, that’s the only switch for the fluorescent, it’s been like that since installed in the late 80s - I was careful to swap the red wires one by one so I didn’t mix them (which was a pain).

What confuses me is that neither PIR is turning the floodlights on - seems unlikely they would both fail at the same time.
 
RealPolitik said:
No, that’s the only switch for the fluorescent, it’s been like that since installed in the late 80s
Click to expand...
Right.
Is there a switch that doesn't do anything or blanked off?

I was careful to swap the red wires one by one so I didn’t mix them (which was a pain).
Click to expand...
Ok.

What confuses me is that neither PIR is turning the floodlights on - seems unlikely they would both fail at the same time.
Click to expand...
It does.

Let's have another photo - you never know.

Do you have multimeter? It's likely to need some testing.
 
No, that’s the only switch there has ever been for the fluorescent tubes and these floodlights - will investigate further in the daylight, thanks again.
 
Maybe I have been looking at this the wrong way round because it looks like a two-way circuit.


Is the switch with all the wires for the outside lights?

Two wires in 1way to the lights for permanently on and
two wires in 2way to the PIRs.

If so then I think you just have the link wire in the wrong terminal in the other switch.

I'll bet the new switch has the triangles the same way up and this has confused you.
 
Last edited:
Yes, the paired wires are for the two floodlights - that makes sense, I will report back...
 
If ,and its a big IF , everything was working well for a week , and the conductors at the switch have not been moved ,then they must be in correct terminals .
 
Think I may have been on the end of some crossed wires - just looked, and I think this is as it should be; right of the picture (L/H switch on faceplate) is for the fluorescent. Floodlights turn on and off OK manually, but I need to get up the ladder to turn down the settings in order to check the PIRs.
 

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So do you now think that things were not working properly for months ? And you are now moving conductors at the switch ?
 
No, that’s as it was, think something may have been miscommunicated to me - one of the PIRs was not working and the time delay on the other seems to be temperamental; I removed the broken one and the other seems (so far) to be working as intended.

Does the switch wiring look as it should?
 
If the outside lights are 'working' with the other switch in the off position, then the wiring would appear to be alright.

Obviously it is impossible to tell from here and with all red wires.



Don't forget, you might have inadvertently screwed one of the terminals on to the insulation instead of the copper, and

there is always the possibility one of the copper cores might have snapped inside the insulation.
This would result in the wire being very floppy at one point.
 
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