How to diagnose fault with lights

OfflerCrocGod

Before you ask, yes I did change the bulb

The kitchen light has recently died and I'm at a loss as to what the problem is. I replaced the light switch (2 gang, 2 way switch) and the other light attached to the panel works fine with the new panel (worked with the old one but the switch seemed jammed/was sparking a bit so I thought it was the cause). I have a screwdriver voltage tester and the live cables are lighting up when I test them, maybe I should test all of them? I'd be surprised if it was a cut in the cable though.

Should I test the light socket with the screwdriver voltage tester? Replace the the light socket?

Any hints as to what to test/replace would be great.

brightspark

You need to be a bit clearer.

Did you replace the switch because it was sticking?

And you still have the same fault remaining?

What points did you test with the voltage tester?

What type of lamp is it?

Bruthal

Swapping switches without confirming the problem can make things worse, unless you are certain you re connected the switch properly.

OfflerCrocGod

I replaced the switch because the light in the kitchen stopped working but just prior to it giving up the switch was sticking and sparked a bit during use. So I guessed the switch was the cause of the issue. I still have the same fault remaining even with the new panel.

I tested one of the COM/L1 connectors just to make sure the voltage tester worked and the power was cut. That might be the one for the working switch. I guess I should open it up tonight and test both COM/L1 wires.

The lamp is a ceiling lamp, simple hanging down wire with dangling bulb socket.

@Bruthal I have in fact made things worse! The downstairs bathroom now seems to have lost power too. I guess the circuits were in series. There was a wire connecting the two L1s in the old switch panel which I didn't use, would connecting the two L1s together fix the issue?

OfflerCrocGod

OfflerCrocGod wrote: »

I guess the circuits were in series. There was a wire connecting the two L1s in the old switch panel which I didn't use, would connecting the two L1s together fix the issue?

Parallel. Yes probably.

Phase testers are a very bad idea, if they get wet or condensation damp can bridge the resistor and give you an unpleasant surprise.

All mains switches spark depending on where it is in the sine wave when you break it, most just do it behind the scenes.

I'd check the wiring to the bulb holder first.

brightspark

Yes the two Coms would normally be connected.

But it is possible that the switch was wired with the live going into the L1 terminals instead.

The missing link is hopefully why the other light isn't working.

Is it a two way lighting circuit? Are the lights controlled elsewhere?



As to your original fault, sometimes one of the pins in the lamp holder sticks, the wire may have come loose.

OfflerCrocGod

Sir Liamalot wrote: »

Phase testers are a very bad idea, if they get wet or condensation damp can bridge the resistor and give you an unpleasant surprise.

Thanks, I didn't know about that. I picked up a screwdriver voltage tester as that's what my dad uses, he lives in Italy so dampness is probably not much of an issue. Would you recommend a multimeter or something else?

Sir Liamalot wrote: »

All mains switches spark depending on where it is in the sine wave when you break it, most just do it behind the scenes.

I'd check the wiring to the bulb holder first.

I guess I can just probe the bulb socket to see if it's live?

OfflerCrocGod

brightspark wrote: »

Yes the two Coms would normally be connected.

In the panel I replaced it was the two L1s that were connected together. Picture of the old panel at this link, two COMs at the top and the two L1s connected.

brightspark wrote: »

But it is possible that the switch was wired with the live going into the L1 terminals instead.

The missing link is hopefully why the other light isn't working.

I'll try and connect them together again tomorrow. When I swapped the panel I moved one wire at a time so I'm fairly confident the wiring is correct.

brightspark wrote: »

Is it a two way lighting circuit? Are the lights controlled elsewhere?



As to your original fault, sometimes one of the pins in the lamp holder sticks, the wire may have come loose.

Nope no L2 wired up and the lights aren't controlled anywhere else. So maybe when I was changing the light bulb a connection came lose or a pin moved and that's the real cause of the issue? Sounds quite plausible.

With the switch on I'd check for 230VAC at the bulb holder contacts with an insulated tool, I'd use a multimeter.

Then turn the supply breaker off.
If you got 230V then check the contacts can mate with the bulb. Sometimes the bayonet caps melt and lose connection edisons can need a good twist sometimes or the centre contact might need pulling up.

If you didn't get 230V check (eyeball + tug test) the wiring into the bulb holder, then wiring into the ceiling fitting.

Are you certain the other light isn't just a bulb too?

Bruthal

It can be fairly tricky to voltage test at a bulb holder with a multimeter at times.

Hence why my DMM probes have a chunk missing come to think of it.

Back probe would be better, if you fancy three trips to the fuse board (off - on -off)

OfflerCrocGod

I tested the multimeter on a socket/car battery and small battery and it gave correct/expected voltage readings on all of those. I wasn't sure which bulb holder contact was live, I could see the wiring and guessed based on it. Tested the contacts and got 0, swapped the probes around and still got 0.

So it looks like there is no power into the bulb holder.

I tested the bathroom bulb holder with another bulb and it's the same as before. It does look like I will need to open up the light panel and wire together the two L1s.

Thanks for all the help guys, appreciate it! Tomorrow I will disassemble the bulb holder and test the wires directly, it's too dark now.

Bruthal

OfflerCrocGod wrote: »

I tested the multimeter on a socket/car battery and small battery and it gave correct/expected voltage readings on all of those. I wasn't sure which bulb holder contact was live, I could see the wiring and guessed based on it. Tested the contacts and got 0, swapped the probes around and still got 0.

So it looks like there is no power into the bulb holder.

I tested the bathroom bulb holder with another bulb and it's the same as before. It does look like I will need to open up the light panel and wire together the two L1s.

Thanks for all the help guys, appreciate it! Tomorrow I will disassemble the bulb holder and test the wires directly, it's too dark now.

Did you test on a 230v socket in the house?

If the multimeter is set to DC, it will read 0v when connected to AC.

It should be set to the highest available AC voltage before the testing.

OfflerCrocGod

eh, yes I found it tricky to test the voltage with the probes but I don't know what a back probe is. I imagine a clip probe would be easiest for testing bulb contacts, clip them on and read with ease.

OfflerCrocGod

Yep I set it to VAC, I tested a socket in the house and it read ~230, used the same settings when testing the bulb holder contacts.

Bruthal

OfflerCrocGod wrote: »

Yep I set it to VAC, I tested a socket in the house and it read ~230, used the same settings when testing the bulb holder contacts.

The live is likely missing so. If the neutral was broke but the phase/live is there, there tends to be a few volts showing on a multimeter.

Open the ceiling rose itself, and test there.

OfflerCrocGod

Tried unscrewing the ceiling rose but it's not coming loose, it's a bog standard one. I imagine I just need more force, or to tap around it with a hammer/screwdriver a bit?

I was wondering if my botched wiring of the light panel might also cause the light to stop working? After all does the panel not control the power to the light? It's just that I'm surprised that the power seems to have gone, it doesn't seem like the sort of thing that just happens naturally?

OfflerCrocGod

OfflerCrocGod wrote: »

what a back probe is..

Just a term of phrase for probing the rearside of a connection rather than the front. In your case the wire terminals inside the holder rather than the bulb contacts.

OfflerCrocGod wrote: »

Tried unscrewing the ceiling rose but it's not coming loose, it's a bog standard one. I imagine I just need more force, or to tap around it with a hammer/screwdriver a bit?

Has it been plastered or painted to the ceiling?
A little leverage may help, they twist off iirc.

OfflerCrocGod wrote: »

I was wondering if my botched wiring of the light panel might also cause the light to stop working? After all does the panel not control the power to the light? It's just that I'm surprised that the power seems to have gone, it doesn't seem like the sort of thing that just happens naturally?

Put it back the way you found it before you test the holder.
Correct, the switch controls the power to the light.
There's a broken connection somewhere.
Electrical entropy.

OfflerCrocGod

Thank you Sir Liamalot, Bruthal and brightspark for your help!

I wired up the two L1s last night and now the lights work.

I'll bring back the multimeter though as the probe wires have already cracked. Very surprised at how cheaply made they are. A Woodies Draper €23 job. I expected a bit more than 2 days use out of it though.

Again thanks for all the help! It's great to be able to see in the kitchen again

OfflerCrocGod

P.S. I used 1.5mm cable, which is the appropriate width according to what I could see, it's only 4 cm long so there should be no problems with the cable.

1.5mm is fine for 10amps.
You don't get a decent and safe multimeter for less than €50.
Uni-T and Amprobe are decent midrange to start off with.