light circuit has stopped working after replacing switch

[alexg]

this is my first post, so be gentle with me!

i've just bought myself a lovely new forest cottage which was owned by a former electrical contractor... the good news therefore is that much of the wiring is new including a new distribution box with rcd's etc...

anyways... to the point...

i have spent the weekend changing the light switches and powered sockets to brass items, earthing the plates where necessary (although in reality 95% of the old ones were already earthed)

in my kitchen i have a 3-gang 2-way light switch which activates two sets of internal lights and a set of two outside lights. the two outside lights operate from the same switch and also benefit from an outside switch.

having fitted a new internal switch, the outside lights are now dead... the outside switch also doesn't work.

i have checked that the new switch is wired up in the same manner as the old (red to common and blue & yellow to the L1 & L2 connectors), but to no avail...

nothing has switched out on the rcd panel... it just appears to have gone dead on me...

...any words of wisdom before i call out a sparky?... (btw.. the bulbs are okay... i did think to check that!)

thanks

 

[electronicsuk]

Either you have a switch that has failed open circuit on both contacts (which seems unlikely on an old switch, never mind a brand new one), or the wiring has become damaged at some point during the work.

There's the third scenario that you haven't actually wired up the new switch in the same way as the old one, but I'll take your word on it. Presumably you also put back in any wire links that were present between terminals on the old one?

 

[alexg]

Either you have a switch that has failed open circuit on both contacts (which seems unlikely on an old switch, never mind a brand new one), or the wiring has become damaged at some point during the work.

There's the third scenario that you haven't actually wired up the new switch in the same way as the old one, but I'll take your word on it. Presumably you also put back in any wire links that were present between terminals on the old one?

many thanks for the reply...

there are only 3 wires for that circuit... red, blue and yellow... and only three connectors on the switch... not sure i could get that wrong if i tried.

there weren't any wire links to the other gangs on the switch.

i suppose the wiring could have broken in the plastic coating when it was being wired up, but surely this would just result in a intermittant connection.

hmmmmmm... i suppose i should see whether i can draw any loose cable through to free up wiring for new connections...

 

[electronicsuk]

It's probably a good idea to rule everything else out before you go to those extents. You could, for example, remove all three wires from the affected gang of the new switch and place them together in a single terminal block.

The expected outcome of this test if the wiring is good would be for the outside lights to be permanently on, you shouldn't be able to turn them off using the other switch on the outside of the house. If you try the outdoor switch and you can control the lights, there is probably a break in one of the strappers (L1 or L2), and if you still can't get any lights on at all then suspect a break in the common wire.

 

[Taylortwocities]

which was owned by a former electrical contractor....

Have you tried putting back the old switch to see if it works with that?
If it does, you can then try it again.

 

[alexg]

thanks for the replies...

i have tried it with the old switch, but it doesn't work... i will try with connector box (5 or 13 amp?), but i guess it sounds like a broken common wire link.

cheers

 

[electronicsuk]

thanks for the replies...

i have tried it with the old switch, but it doesn't work... i will try with connector box (5 or 13 amp?), but i guess it sounds like a broken common wire link.

cheers

You'll find it easier to get all 3 wires into a 15A choc block.

 

[alexg]

if it doesn't work, then can i link across a common wire from one of the other (working switches)?... or will this result in a light that only works when the other switch is activated?

sorry... bit dim with these things...

lastly... does the earth wire have any physical function in the equation other than to stop me nuking myself if i stuff up...?

having spent most of the weekend fitting nice new earth wires from the socket casings to the plates, i'm now sick to the sight of stiff inflexible green & yellow bloody wires!

 

[alexg]

well, i tried connecting the red to the blue & yellow via a connector block and the lights still don't work.

i have one of those neon screwdrivers, but haven't a clue how to safely use it... just thought it might help in working out whether the red is still live or whether it has been broken...

sorry to be so retarded... but i always think it's better to ask the most simple of questions in order to get the most simple answers (ie. ones that won't confuse and then kill me! lol)

cheers

 

[Taylortwocities]

Sounds like the red blue yellow cable is a two way switch (is there another switch for those lights somewhere else).

Neon screwdrivers are as much use as a chocolate teapot but more dangerous.
Throw it away. It will not help.

Its impossible to advise you. Best get a spark in.

 

[alexg]

it is a 2-way switch as there is also an outside switch for the two outside lights...

by using a process of elimination...

a.) i haven't touched any of the outside lighting or the outside lighting switch
b.) the lighting is on a rcd circuit which is active and does not trip out
c.) the bulbs haven't blown
d.) all i have done is changed the switch
e.) it's not the switch as i've bypassed this with a connector block (red connected to yellow & blue).

so what can it be?

quick question....

can i use any of the common (red) connections from the other light switches... if this technically works, i could check whether the common connection is the problem... once this is done, surely it is a question of the yellow or the blue... in which case, how do i check that?

cheers

 

[dannyboi2003]

Can you post a pic of the light switch and wiring as it will help clarify things a bit. No offence intended but if everything worked up until you changed this switch then you must have wired something wrong or disturbed something.

Like i say a picture will help immensely.

 

[electronicsuk]

At a guess I would say no, you can't tap off anywhere else on the switch. You say you're certain that there were no link wires present on the old switch, therefore it's sensible to assume that live supply to the two-way circuit for your outdoor lights comes from the outdoor switch.

Two-way switching relies on the common being connected to the remote switch, it wont work otherwise. If you're going to take pictures then it would also be prudent to open the outdoor switch and take a photo of the wiring in there, as the number of cores in there will be a good indication as to whether there's a hidden junction box somewhere.

Also, if the switch is in a dryline wall then it may be worth pulling out the dry lining box and checking behind it for extra wiring. I have a number of switches in my house where further connections had been made behind the box in terminal block, presumably because the original installer was too lazy to neaten things up so they fit in the box. If you had a similar setup then something could have worked loose when you changed the switch.

 

[Space cat]

If I have read this whole thread correctly, this switch has only three wires in it: red, yellow and blue. I would guess that these are all in the same cable. True or false?

If it's true then power for that outside light must come from somewhere else - or not in your case! If you're absolutely sure that no link wires fell out while you weren't looking, you will have to find out where the power ought to be coming from.

Are you sure that the outside light is on the same circuit as the others? Since its wires are in the same switch box as the inside lights, it really ought to be on the same circuit - but what is and what ought to be are two entirely different things!

I think you'll have to do some detective work here and that will mean testing circuits for the presence or absence of volts! A proper neon driver can help if you know how to use it. The ones that have a battery and LED in them are fit only for testing fuses. Meters are not expensive but, as with neons, you have to know how to interpret the results. Many a DIY electrician has been fooled by a meter that read a hundred volts or more on a wire not actually connected to anything!

As a first test, I would put the three wires back into the choc-block and, with power on, carefully test for voltage on the block.

 

[sm1thson]

heres a thought, could the light you are working on be on an FCU (fused connection unit) the work you have done may had blown this fuse rather than tripping anything in the CU? just a stab in the dark, all I can do without been there!