A puzzling fault

[The Dentist]

My Dad called me yesterday with a fault that I cant figure out

He has a halogen exterior light which was tripping the lighting mcb when switched on, he disconected it at the switch by removing the link wire which came from the live feed to the other switch in the box - this was 10 years ago!

Yesterday he called me as he had noticed that the halogen light was glowing a dim red, he hadn't noticed it before, but I can only assume it's been like this since the fault

As the live is disconnected at the switch, I'm guessing the light must somehow be receiving voltage either via the original fault through the N, and has a very high resistance path back to earth, possibly from water ingress or suchlike?

I'm going over to sort the fault over xmas, and I'm hoping the fault will be obvious once I start investigating, but it has me a bit stumped as to what might be happening here - any ideas?

The supply is a TT

Thanks, and Merry Xmas

 

[The Dentist]

Any ideas anyone?

Someone must have come across this type of problem before

 

[bernardgreen]

More information needed.

What wattage is the lamp ?

Does it have a PIR sensor ?

Do any other lamps or appliances act strangely as a dimly glowing lamp can be the result of the lamp being in series with something else.

Glowing dimly is unlikley to be due to a leakage through moisture.

If the lamp is wired (incorrectly when it was dis-connected) across a switch for another lamp then when the switch is OFF the two lamps will be in series across 230 volts and both will glow, how much each lamp glows depends on the relative wattages and types of the lamps.

Some external automatic lamps have a ballast that keeps the lamp pre heated to reduce the thermal shock when the lamp is turned on. It also prevents condensation in the lamp. Unlikely in a domestic lamp but not impossible.

 

[The Dentist]

Can't be 100% sure until I visit, but think its a basic 500w halogen, no pir, was just operated by the switch (which is now disconnected). Nothing else acts peculiar afaik

Thanks for the reply Bernard, will post the outcome in the new year

 

[martinxxxxxx]

So the lamp has one end connected to a wire that is open circuit from anything (as it used to be connected to a switch to the live supply and has now been removed from the terminal) and the other end is still connected to neutral as it was wired through a lightswitch (as opposed to a FCU)

Right; if this is correct , then something is perhaps bridging the disconnected live wire (such as a dead mouse or a dead slug, seen both in last 2 weeks across electrical terminals).

Either that or Santa dust has got in the works