Light fitting tripping RCD

[Bobby'sGirl]

Hi all,
Firstly a very happy New Year to all!

We recently bought a century old police house that's needing a fair few wee things doing to get it up to speed.

We have a lot of DIY experience and are working on a limited budget so everything we can safely do ourselves we will. Usually have no issues putting in new light fittings and have replaced many over the years, making note of how it's already wired and replicating to the new fitting.

This one's got us stumped though.

It bangs and blows each time the switch is flipped.

There's one live (old red) and one switched live (old black) and earth in the wall switch and same to the light fitting.
The fitting we are replacing just had 2 standard lighting fitting wires to a terminal block and that was working fine before removal.

New fitting has blue, brown, green to terminal block.

Couldn't follow directly the original fitting as the wires weren't colour coded but have now tried - live and switched live - both ways around but both ways blow.

Maybe of interest is that the new light fitting is a barely used good quality 2nd hand one with a metal body but had the earth wire unscrewed from the terminal block - which we put back in before attempting to install.

Any ideas on why it's just not a happy camper?
Was assured by the seller that the fitting worked perfectly and only removed to sell as they were selling the house and putting in standard bulb holders.

 

[Jock from the north]

Hi all,
Firstly a very happy New Year to all!

We recently bought a century old police house that's needing a fair few wee things doing to get it up to speed.

We have a lot of DIY experience and are working on a limited budget so everything we can safely do ourselves we will. Usually have no issues putting in new light fittings and have replaced many over the years, making note of how it's already wired and replicating to the new fitting.

This one's got us stumped though.

It bangs and blows each time the switch is flipped.

There's one live (old red) and one switched live (old black) and earth in the wall switch and same to the light fitting.
The fitting we are replacing just had 2 standard lighting fitting wires to a terminal block and that was working fine before removal.

New fitting has blue, brown, green to terminal block.

Couldn't follow directly the original fitting as the wires weren't colour coded but have now tried - live and switched live - both ways around but both ways blow.

Maybe of interest is that the new light fitting is a barely used good quality 2nd hand one with a metal body but had the earth wire unscrewed from the terminal block - which we put back in before attempting to install.

Any ideas on why it's just not a happy camper?
Was assured by the seller that the fitting worked perfectly and only removed to sell as they were selling the house and putting in standard bulb holders.

Hi there if you have a simple continuity tester or something similar you could with fitting disconnected and on the ground test between the earth that was disconnected and the brown wire.if you get continuity or a low reading then it will be the light that is damaged .polarity shouldn't matter for light to work although is important to get it right especially if its screw in bulbs .could you send pics of light and wires at ceiling
Thanks
When you say live and switch live do you mean switch live and neutral

 

[Jock from the north]

Hi all,
Firstly a very happy New Year to all!

We recently bought a century old police house that's needing a fair few wee things doing to get it up to speed.

We have a lot of DIY experience and are working on a limited budget so everything we can safely do ourselves we will. Usually have no issues putting in new light fittings and have replaced many over the years, making note of how it's already wired and replicating to the new fitting.

This one's got us stumped though.

It bangs and blows each time the switch is flipped.

There's one live (old red) and one switched live (old black) and earth in the wall switch and same to the light fitting.
The fitting we are replacing just had 2 standard lighting fitting wires to a terminal block and that was working fine before removal.

New fitting has blue, brown, green to terminal block.

Couldn't follow directly the original fitting as the wires weren't colour coded but have now tried - live and switched live - both ways around but both ways blow.

Maybe of interest is that the new light fitting is a barely used good quality 2nd hand one with a metal body but had the earth wire unscrewed from the terminal block - which we put back in before attempting to install.

Any ideas on why it's just not a happy camper?
Was assured by the seller that the fitting worked perfectly and only removed to sell as they were selling the house and putting in standard bulb holders.

In order for light to work it dosnt require a live ,just a switch live [red] and a neutral [black] when you say there is a black connected to wall switch that would suggest its wired in a loop in method and you may simply be short circuiting sw live to neutral at light .would only know with a photo

 

[Bobby'sGirl]

Hi there if you have a simple continuity tester or something similar you could with fitting disconnected and on the ground test between the earth that was disconnected and the brown wire.if you get continuity or a low reading then it will be the light that is damaged .polarity shouldn't matter for light to work although is important to get it right especially if its screw in bulbs .could you send pics of light and wires at ceiling
Thanks
When you say live and switch live do you mean switch live and neutral

Hi Jock ftN,

Don't have a tester unfortunately, but had a brainwave and wired the fitting up to a plug to see if behaved the same.
Immediately blew again soon as switch flipped.
So know it's not the lighting circuit.

Could definitely try the test between the earth and brown wire but have to get a tester - which may be worth doing as the fitting is nice and works well in the room it was intended for.
If we establish a fault, is it a rewire of the fitting or discard?
Seems such a shame if it can't be saved, it's a lovely light.
Must have it safe though as the room it's to be used in will be my mum's who has dementia so safety a priority.
Not at home but can post pic when I get back.

 

[Jock from the north]

Hi Jock ftN,

Don't have a tester unfortunately, but had a brainwave and wired the fitting up to a plug to see if behaved the same.
Immediately blew again soon as switch flipped.
So know it's not the lighting circuit.

Could definitely try the test between the earth and brown wire but have to get a tester - which may be worth doing as the fitting is nice and works well in the room it was intended for.
If we establish a fault, is it a rewire of the fitting or discard?
Seems such a shame if it can't be saved, it's a lovely light.
Must have it safe though as the room it's to be used in will be my mum's who has dementia so safety a priority.
Not at home but can post pic when I get back.

Yeh I suppose it depends on if the fitting can be rewired ,yeh if you post a pic of cables at light and light switch that would clear things up .
Thanks

 

[westward10]

It has a fault to earth hence why the earth had been disconnected, in this state it would have been very dangerous if connected. With the earth connected the circuit was acting correctly and disconnecting the circuit. Where did it come from?