no power to cables behind light switch

[BS3036]

between the live wire and the switch wire.. there is a path back to the neutral through the lamp..

Not if the lamp fails or is removed.

For the timer to fail in reasonably to be expected circumstances is unacceptable, and the design should never have been made.

You know, quite a lot of timers are backed up by rechargable batteries. I don't see the difference myself.

 

[ban-all-sheds]

IMO there's a big difference between having battery back up and relying on a current path with no known reliability or QOS standards.

In a nutshell, making a product which needs a working lamp of a particular type to remain in the circuit to supply current to the product is shoddy and offensive engineering.

 

[bongos]

It sounds like your live feed to the switch has gone open circuit/broken.

Confirm that you have 230v between the live loop and neutral/earth in the light fitting. If this is the case then it should confirm the break in the live feed to the switch.

 

[Jacobssi]

I was tought 0 means short circuit . >999 means open circuit. so is this the other way round?

Does it?

0V between either of the switch conductors and earth means a short circuit?

I think not.

Jack - you need to find where the switch cable comes from - the red should be permanently live, and clearly it isn't.

One thing which puzzles me - hadn't thought about it before - how does the timer work with no neutral?

 

[BS3036]

I was tought 0 means short circuit . >999 means open circuit. so is this the other way round?

Does it?

0V between either of the switch conductors and earth means a short circuit?

I think not.

Jack - you need to find where the switch cable comes from - the red should be permanently live, and clearly it isn't.

One thing which puzzles me - hadn't thought about it before - how does the timer work with no neutral?

You see, the meter is set to measure ac volts, not ohms. Also if you set the meter to measure ohms, and then connect it to a circuit which might have 230V ac, you are likely to damage the meter.

But absence of volts does not imply a short circuit, just a lack of volts.

 

[Jacobssi]

Am I getting confused with insulation resistance testing?

 

[ban-all-sheds]

I don't know - the meter was set to an AC volts range, and measured 0V between each of the switch wires and earth. That wasn't an IR test....

 

[Jacobssi]

I understand that wasn't an IR BAS but I am asking, what I thought the results showed I'm getting confused with another test. But don't worry. Its Continuity of earthing conductor Im getting confused with.

 

[bongos]

I was tought 0 means short circuit . >999 means open circuit. so is this the other way round?

You are mixing up resistance with voltage.

0Ω between two conductors suggests a short circuit.

∞/OL/>999MΩ between two conductors suggets an open circuit.

But there has not been a measure of the resistance of the circuit. There has been a measure of the voltage between the live switch feed and neutral/earth. There should be ~230vAC between live and neutral/earth but there is 0v, suggesting a break in the live switch feed.

 

[ban-all-sheds]

Or the earth core is connected to nothing at the other end...

 

[GreenElectrics]

Looks like the wiring goes back to junction boxes.

The problem either lies in a damaged cable to the switch or a broken termination in the junction boxes.

Typically, all the junction boxes would all be located in one central place for the downstairs lights (usually under the landing floorboards).

 

[ban-all-sheds]

How can you tell that on the basis of a photo of the wiring to one switch?

 

[GreenElectrics]

How can you tell that on the basis of a photo of the wiring to one switch?

Hi BAS,
I stand corrected, of course it could be using the loop-in method, which would mean a permanent live, neutral and earth at the light fitting with a live, switched live and earth going to the light switch.

I made an assumption, (which remains to be disproven) so thanks BAS for pointing this out, or do you have another theory?

 

[bernardgreen]

Looks like the wiring goes back to junction boxes.

Makes sense.

Typically, all the junction boxes would all be located in one central place for the downstairs lights (usually under the landing floorboards).

Or more likely the junction boxes are dispersed around the house and cunningly camaflaged as ceiling roses with a set of three terminals......

As to charging the timers battery for keeping the clock running. Only a few micro-amps are needed for the clock so only a couple of seconds of 230 volts across the switch terminals will put enough charge in for several days if not weeks. Battery wrist watches can run for years on a minute battery. It is true that if the lamp has been removed or has blown then maybe after a few weeks the timer will stop but if no working lamp then no need for the timer to operate.

 

[ban-all-sheds]

I stand corrected, of course it could be using the loop-in method, which would mean a permanent live, neutral and earth at the light fitting with a live, switched live and earth going to the light switch.

The switch drop cable would be the same.

I made an assumption, (which remains to be disproven)

Or proven

so thanks BAS for pointing this out, or do you have another theory?

Doesn't matter right now what's at the other end of that switch cable, what matters is finding the other end and establishing why there's no permanent live reaching the switch.

If there is an Octopus in good nick it might be worth money