Can't make sense of faulty dimmer switch wiring.

[RobCardiff]

Hello. I'm trying to fix a faulty dimmer switch but can't make much sense of the way the previous owner wired it. There are two dimmer switches on the plate controlling two separate lights. One of the lights turns on and off and dims no problem. The other switch turns the light on but only allows it to be very dim. I've switched the bulbs around with the same result so I know the bulb is fine.

I want to check that the existing switch is wired properly before I try a new one but the wiring doesn't match anything I can find online. Does this look right or make any sense to anyone (please see pic)?

Any help appreciated.

 

[gman76]

Hi Rob,

That looks like a bit of bodge job - why have you got an unterminated CPC & where does it go?

Can you take another picture at 90 degrees to that one so we can see inside the back box please?

 

[RobCardiff]

Hi Rob,

That looks like a bit of bodge job - why have you got an unterminated CPC & where does it go?

Can you take another picture at 90 degrees to that one so we can see inside the back box please?

Hi Gman. I'm sure it is a bodge job - the guy I bought the house from seems to have done a lot of his own work and I'm not convinced he knew what he was doing. Anyway, I've attached another picture. I don't know why there is a wire hanging loose, it was like that when I opened it up. Thanks.

 

[EFLImpudence]

What is your confusion?

You have power to both L1s and the switched lives from the wavy line symbol presumably to the two lights.


As above, connect THE CPC(earth wire).

 

[RobCardiff]

What is your confusion?

You have power to both L1s and the switched lives from the wavy line symbol presumably to the two lights.


As above, connect THE CPC(earth wire).

Hi. I wanted to check that it was wired correctly because it didn't seem to match any diagrams I found online. If it's wired correctly I will replace the switch with a new one and wire it the same way. Where does the CPC go?

 

[EFLImpudence]

Where does the CPC go?

In the earth terminal on the switch with the green and yellow wire.

 

[gman76]

With the power off (check for dead), terminate the CPC as EFLI says, then swap the larger single grey wire at the top of the switch with the single red wire at the bottom.

That should change which light is operated by which switch & reveal whether the dimmer is faulty.

 

[RobCardiff]

With the power off (check for dead), terminate the CPC as EFLI says, then swap the larger single grey wire at the top of the switch with the single red wire at the bottom.

That should change which light is operated by which switch & reveal whether the dimmer is faulty.

I switched them around and now the fault has gone to the other light so it does look like a faulty switch. I'll get a new switch and wire it the same way. Is there anything else that looks dodgy to you or was it just the earth hanging loose?

Thanks for your help - and EFLImpudence too.

 

[gman76]

Hi Rob,

When you replace the switch fit a grommet in the back box where the cables enter & make sure everything is terminated nicely (including the CPC to the back box) without any exposed copper.

From your original picture, I thought that someone may have over-sleeved the CPC from the twin red cable & used it as a live conductor, hence my bodge comment - but it appears to be a double insulated single, so all good.

 

[RobCardiff]

Hi Rob,

When you replace the switch fit a grommet in the back box where the cables enter & make sure everything is terminated nicely (including the CPC to the back box) without any exposed copper.

From your original picture, I thought that someone may have over-sleeved the CPC from the twin red cable & used it as a live conductor, hence my bodge comment - but it appears to be a double insulated single, so all good.

Hi Gman. Thanks for your advice. I changed the switch and wired it up exactly the same as before but it's still playing up. Both lights now dim but one of the dimmer switches now controls both lights. The other dimmer will control it's designated light, but only if the first switch is on. I don't expect you to work this out for me, you've already been very helpful, but do you have any ideas what might be wrong? Thanks.

 

[gman76]

Sounds like you've got some wires mixed up - post another pic of how it is wired now.

 

[RobCardiff]

Sounds like you've got some wires mixed up - post another pic of how it is wired now.

Here it is....

 

[gman76]

Ok, my best guess is that the two reds from the same cable are the wrong way round, but the strapper between the two modules is in the correct place.

Swap them around.

 

[RobCardiff]

Ok, my best guess is that the two reds from the same cable are the wrong way round, but the strapper between the two modules is in the correct place.

Swap them around.

That did the trick. The lights are flickering a bit and the switch is buzzing but that might just be because I bought a cheap Wickes light switch. I think it's wired up correctly now at least. Thanks very much, have a good night

 

[333rocky333]

What lamps are you dimming, you have bought a dimmer with a 60w minimum load, nowadays with leds that may not be suitable