Lighting circuit trips plug circuit

We had our house rewired 18 months ago, and about 6 months ago the light stopped working in the main bedroom, for about a week, then it began working again. Then last week it stopped. It is a single switch with earth attached.

1. I firstly tried changing the bulb for one that definitely worked, but this didn't sort it.

2. I then isolated the upstairs lighting and checked both the light switch and the bulb housing - all wiring appears to be ok, no scortch marks, all connected, all screws touching the copper, not the insulation. I have also tried changing the light switch over with one from another room upstairs that still works, but this didn't sort the problem.

3. My father-in-law came over with his volt meter thing in the week and there appears to be no current to the light switch. The volt meter does not plug in to a plug socket. After he had left my wife noticed that the upstairs plug sockets had tripped (separate isolator on the mains).

Anyone have any advice on what could be the issue, or should I just bite the bullet and get the electrician back round?

What cable(s) do you have at the switch?

Just a single brown/blue twin & earth, or 2 or 3 with all the blues in a connector block?

How many cables at the light fitting? Just one, or 2 or 3?

There shouldn't be any link between the lighting circuit and the sockets, so you've got 2 separate problems, unless....

What do you mean by "separate isolator on the mains" - was it the breaker for the sockets which tripped, or an RCD covering both the sockets and the lights?

A picture paints a thousand words.

The breaker circled on the left was the one which tripped, but the one on the right controls the upstairs lighting.

The back of the light switch

The light its self.

Looking at it, I'm guessing that the power comes to the light first, then the second wire links the light to the switch on the wall, so perhaps its the light its self that is broken?

Plug issue seems to have been coincidential - a lose wire in the plug.

Looking at the picture of the switch that excess copper would worry me.

There should be no copper on show in the back box.

I will assume that you have not removed the switch at some stage.

You say that your father in law found no voltage at the switch. I take it he tested both sides of the switch and activated the switch itself.

Have you considered that the switch could be faulty - try changing the switch to one you know works - don't forget to safely isolate the circuit first.

Did your father in law check if there was voltage at the ceiling rose loop and at the ceiling rose switch live?

If you have voltage here and definitely no voltage at the switch then you either have a break in the cable or the switch is at fault.

I've tried changing the switches but without success.

My father in law tried volt testing the switch with the mains on, but I'm not sure if he tested both sides. He didn't test the ceiling rose loop - where abouts on the rose do I need to test?

I have that nasty feeling in the back of my head that this problem is going to cost me!

Ben298 said:

I've tried changing the switches but without success.

My father in law tried volt testing the switch with the mains on, but I'm not sure if he tested both sides. He didn't test the ceiling rose loop - where abouts on the rose do I need to test?

I have that nasty feeling in the back of my head that this problem is going to cost me!

Click to expand...

The middle three brown is the live loop, one of those goes goes to the switch and back to the two brown (the one linked to the pendant).

Cost depends if it is just one light I can't see it being the lighting loop so if it is the switch cable that could be an issue if it needs to be removed from a plastered wall if you can't just slide it out.

My guess is it is the pendant has broken at the other end from the rose.

And get some green / yellow sleve on the earth in the back box asap.

On a second look you might just need to clip the excess.

If you are not sure how to test the voltage at the ceiling rose ask your father in law to come back around and test it for you. If there is power there then...

As suggested check/replace the pendant to see if there is a problem there.

If there is still a problem and your father in law's meter is a multi meter do a continuity test on the switch wire. Assumption is made here that you have correctly identified which of the two cables is the 'line' and which is the switch live.

This is a dead circuit test - so make sure the circuit is de-energised before you start and remove the lamp.

At the ceiling rose identify the switch wire and connect together the two brown cables with a terminal block.

Set the meter to low ohms - null out or test the meter leads.

At the switch test between the common and L1 terminals (or those that have the brown cables in). Because you have created a loop you should get a reading in ohms. If you do not get a reading then flick the switch - this should either stop continuity or allow it - depending on which way the switch is set up.

If you have the equipment you should also do a test for insulation resistance to test the integrity of the cable.

If you can identify that continuity exists within the switch wire then the problem may lie elsewhere - either at the ceiling rose or the pendant.

You can do a similar continuity test with the removed pendant by connecting its line and neutral wires together and testing across the line and neutral in the bulb holder.

You could try looking in the loft to see if the switch wire has been damaged. Look closely the whole length.

Also, check for nails in wall for pictures.