Please help to resolve the mystery of light bulb

[Zehroni]

The outside light works from pull down switch in the porch. It has been like that since we moved into the house - 3 years ago. It has suddenly come on today and it does not switch off even if I turn the switch off. I initially thought the switch is faulty which I have just replaced it with a new pull down switch but it is still on, no matter what I do. I have also tested the two wires going into the switch and to my surprise both are live. I was expecting only one of them is live and the other one (the one goes the bulb) becomes live when the switch is on.

Ant help to troubleshoot and resolve this problem would be highly appreciated.

 

[big-all]

do you have rats mice or other gnawing pests ??
any diy or other work in the house??

 

[Zehroni]

Many thanks for the speedy reply. I do not have pets at all. But I do live in a big four bed house next to a filed

 

[PrenticeBoyofDerry]

How did you test, what readings did you get and what instrument did you use to prove this?

 

[Zehroni]

I disconnected both wires from the switch and tested them with a neon testing screwdriver.

 

[Taylortwocities]

The picture below indicates the best place for the neon screwdriver.
Neon screwdrivers lie, are unreliable and cannot be used to trace faults.

Untitled

• Taylortwocities
• 11 Feb 2009
• 20

You meed a two probe voltage test device or a multimeter.
Let us know when you have one of these.

 

[AndyPRK]

Is it giving an incorrect reading this time do you think?

 

[Zehroni]

I have a multimeter

 

[PrenticeBoyofDerry]

I have a multimeter

That is best used to test for voltage rather than an neon screwdriver(not a device that can be trusted to give you satisfactory readings)
A device that can measure a value, would be more helpful.

 

[ekmdgrf]

The outside light works from pull down switch in the porch. It has been like that since we moved into the house - 3 years ago. It has suddenly come on today and it does not switch off even if I turn the switch off. I initially thought the switch is faulty which I have just replaced it with a new pull down switch but it is still on, no matter what I do. I have also tested the two wires going into the switch and to my surprise both are live. I was expecting only one of them is live and the other one (the one goes the bulb) becomes live when the switch is on.

Ant help to troubleshoot and resolve this problem would be highly appreciated.

As you say the wire goes from the switch to the lamp, so if the lamp is on, then the wire will be live. Even if it happens that the switch is disconnected. Obviously it shouldn't be that way, so there is a fault somewhere. Likely somehow the permanent live has shorted to the switched live and so is acting like the switch. As already stated, maybe it has a rat/mouse/bob cat attached to it, or a screw/nail/router bit stuck through it. I'd start by checking the lamp to see that everything is in order and also the JB is one is used. Most likely you'd have to get your coveralls on and play "hunt-the-cable". Good luck with that.

 

[dannyboi2003]

Does the outside light have a PIR sensor on it? With the pull cord being the over-ride switch for it.