Double dimmer switch fault, help please!

[gertybertyangel]

Hi,

Apologies for the long post, just want to explain fully!

I have 2 lights in my kitchen, one over the main kitchen area and one in the diner area. Both light fittings are dimmable and have 6 halogen bulbs in each fitting. Fitting and dimmer switches were put in about 3 years ago and not touched apart from bulb changes.

About 2 weeks ago I turned on the kitchen area dimmer as usual and one of the bulbs blew, tripping the circuit as has sometimes happened before.

I reset the RCD to see which bulb had blown but no bulbs came on at all (The diner fitting was fine). Thinking there was a fault with the fitting, I swapped a couple of (knowingly working) diner bulbs over to the kitchen fitting to try to prove that theory and as expected, nothing happened. So, I took a good look at the kitchen light to see if a wire was loose but all looked and felt normal.

I decided to switch the wires around in the double dimmer switch and then the kitchen one worked, but the diner one didn't - making me think that the switch must be at fault, as both lights operated (but not together - are you following this? haha!)

So, I got a replacement double dimmer today, wired it up as it was wired PRIOR to me rewiring it the other way around (I had it all written down before I touched it, just to be sure) and the same thing has happened - it will only operate one light.

I'm guessing there is a fault with the wiring at the switch, but cannot understand how it's occurred as nobody touched the wiring prior to the fault - no decorating has been done to loosen the switches or anything.

Wiring as follows:
Kitchen side - red with white sleeve to common
- black with red sleeve to L1

Diner side (this is also operated on another switch by back door, but that hasn't been touched either) Red to common
Blue to L1
Yellow to L2

There are earths screwed into the metal box and also the metal dimmer.

Any ideas really appreciated! Thanks

 

[EFLImpudence]

Does the new switch work the other light if you change the wires around again?

Not unknown for 'new' products to be faulty.

 

[gertybertyangel]

Hi,
Yes the same thing happened as when the old switch was in which is why I'm stumped!

 

[ericmark]

I am going to try to work out what may be wrong by going through the steps I think you have taken.

You say swapping wiring at switch means the fault swaps to other lamp so there seems to be just two possible scenarios.

One the replacement dimmer is faulty.

Two if you only swapped the output from switch then you have lost supply to switch.

The red, yellow, Blue cable would be standard colours for the second switch of a two way system L1 or L2 will be line and the other will be switch wire likely if you look at other switch you will see two cables go into L1 and L2 with a single wire (red) in the com.

Again for non two way using Com and L1 also seems correct.

Had the two way switch failed I would be looking for where the dimmer is actually installed but seems it’s the simple on/off which is the problem. I had also considered leading and lagging inverters if 12 volt lighting is used but can’t see how swapping side to side of switch would then allow it to work.

If it were me I would at least temporary fit a standard 2 gang 2 way switch and see if this cures the problem. In fact quartz halogen lamps should not be dimmed anyway. They rely on the quartz being that hot that the tungsten will not be deposited on it but will return to the element running cool reduces the lamp life. With extra low voltage types you have an inverter specially designed to maintain the voltage at exactly the right level to prolong the lamp life adding anything to defeat this would be rather silly. Yes I know people do fit dimmers but I would always use low voltage (230v) with dimmer not extra low voltage (12v) you don’t say which type you are using.

 

[securespark]

Was going to say.

Put the switchwires together with their respective feeds and see if both lights fire up.

 

[gertybertyangel]

Thanks for the replies so far, am gonna give it a go again in a bit or tomorrow - thank goodness we still have light nights so I can see what I'm doing!