Lighting fault

themoog · Post by **themoog** » Wed Dec 27, 2023 11:53 am

Hi everyone and merry Christmas etc.
My utility room has a centre ceiling led light and led strip light under the units. Both are operated from a double 2 gang plate. For some reason the other day the strip lights failed to turn on.
The main light is ok but the switch that operates the strip lights shows only 1.3v across the terminals either on or off.
Is the switch toast or should I be looking for something else?
Thanks

Someone-Else · Post by **Someone-Else** » Wed Dec 27, 2023 1:30 pm

Measuring across light switch terminals is not the way to go, you need to check between Live and Neutral for a voltage. If an LED strip does not work, check the voltage going to the actual strip or the driver for the strip.

themoog · Post by **themoog** » Wed Dec 27, 2023 1:32 pm

There is no power to the led transformer. I did measure between live and neutral (or so I thought) on the switch.

Someone-Else · Post by **Someone-Else** » Wed Dec 27, 2023 3:10 pm

The obvious question has to be where is the power supply fed from?
Pictures would help

OnlyMe · Post by **OnlyMe** » Thu Dec 28, 2023 9:57 am

As SE says. You need to check at the driver not the switch. Often the driver is on top of a kitchen cupboard

stevei · Post by **stevei** » Thu Dec 28, 2023 4:49 pm

themoog wrote: ↑Wed Dec 27, 2023 1:32 pm I did measure between live and neutral (or so I thought) on the switch.

There isn't a neutral at the switch. The two are live and switched live (out). That's why you need to check at the transformer.

themoog · Post by **themoog** » Fri Dec 29, 2023 2:51 pm

Baffled.. replaced the switch. Still the same. Been up in the roof space above to check the wiring and my Fluke meter shows only 2.5v on the feed from the main consumer unit in the garage which fortunately is only a few meters away. No power to the led drivers either. I have a cable voltage tester and I noticed that when I touched the earth / switch back box it bleeped showing voltage - and in fact one of the rcds tripped last week when I unplugged the Dyson from a socket in the kitchen. Could that be the cause? The Fluke didn’t show 240v on the earth cables though so I don’t get that.
All other lights in the house work correctly so it can’t be the Mcb. The evidence points to a broken cable but the same cable is part of the utility/ kitchen and hall ring so it can’t be.
Now I’m not a qualified electrician but a general builder by trade so I have some knowledge but this has thrown me and I want to understand.
Don’t panic - I’m not going to have a go anymore and I’ll get a mate in who’s a sparky to take a butcher’s but if anyone can shed light (no pun intended) on this it would be great.

Someone-Else · Post by **Someone-Else** » Fri Dec 29, 2023 3:59 pm

There is your problem.

themoog wrote: ↑Fri Dec 29, 2023 2:51 pmFluke meter shows only 2.5v on the feed from the main consumer unit

themoog · Post by **themoog** » Wed Jan 03, 2024 12:25 pm

Yes but how can that be if it’s part of the lighting ring and everything else works ok?

Someone-Else · Post by **Someone-Else** » Wed Jan 03, 2024 1:29 pm

Science, lighting circuits are not wired in a ring, you are probably picking up an induced voltage.

themoog · Post by **themoog** » Mon Jan 08, 2024 4:04 pm

Fixed. Turns out, unbeknown to me, when I installed the leds years ago I took the feed from a cable in the loft which also feeds an old outside bulkhead light which we have never used - which has its own switch in the garage. That switch has never been touched by us. Someone must have accidentally flicked the switch off which in turn stopped feed to the leds in the utility. The wife did it I reckon.
Nothing to do with me when I was connecting up all the outside Xmas lights I’m sure..