New light keeps blowing in bathroom (with pictures)

[Wannabe Plumber]

Hello everyone,

I’ve done a lot of DIY on our 1910 terrace house since moving in nearly two years ago. Simple thing is electrics scare me.

I have just finished doing the bathroom, and changed the light for a nicer halogen frosted effect light (240V 40W). However, now the light keeps randomly blowing the bulb and so I’ve opened up the light and and was wondering if you could give me some advice on the wiring:

The middle (B) is earth looped together from all three sets of wires (I will cover it in green and yellow tape) A is the live (red) for wires 1 and 2 and C is the live for cable 3. D is the black cables for all three cables taped together.

I have a pull switch at the entrance to the bathroom, and an extractor fan that runs independently from its own pull cord, whether or not the bathroom light is on (so when the light blows the bulb the extractor fan still works – and I know it’s on the lighting circuit coz when I trip the lighting fuse downstairs the fan doesn’t work)

www.lindles.f9.co.uk/diynot/Wiring.jpg

With the light switch pull cord off, electrical testing between A and C gives nothing, Between B and C gives nothing and between A and B gives 238V

With the pull cord on, testing between A and C gives 238V, as does A to B (earth), but again B to C gives nothing.

When wiring the new light I did (in my ignorance) earth to the earth, A (the two reds) to Brown and C to Blue

Is the wiring right, is how I've connected to the new light correct and if so why is my light blowing the bulb?

Many thanks in advance.

 

[breezer]

the image link you have typed is wrong

 

[Wannabe Plumber]

the image link you have typed is wrong

Have now stuck in correct links.

Cheers breezer

 

[Belle427]

you need to identify the switch cable,it looks as if you have mixed them up,do you have a multimeter?

 

[Wannabe Plumber]

you need to identify the switch cable,it looks as if you have mixed them up,do you have a multimeter?

I haven't done anything to the actual cables. I just took off the old light and replaced it with a new one (using A to Live, B to earth and C to Neutral)

If by Multimeter you mean the yellow box, with LCD and red and black pointers that I can use to test the voltage then yes. What do I do with it to find which is the switch cable (I was thinking that the switch cable was the second in the photo the one with cable C coming out of it, as it's only active when I pull the switch cord.

Sorry, really don't know anything about electrics.

Thanks for helping.

 

[dannyboi2003]

I've had a good look at the picture and I think your pull cord is switching the neutral to the light on/off and not the live.

This is how I think it should be wired, but before you do anything I’d trim all that scorched cable off and strip off and make fresh connections, as it stands the insulation looks very brittle and has begun to crack.

Anyway the wiring...

Firstly isolate the mains supply, in this situation I would turn off the main switch for the entire house and not just the breaker/fuse for the lights.

C and the black lead in the same cable that goes to D is your switch cable, disconnect this and move it to one side, you now have two T&E (twin and earth) cables with 2x red, 2x black and 2x bare earth. This is the mains feed in from your previous fitting and outgoing feed to the next light fitting. Join all the reds together in their own terminal block (including the one on the switch wire we set aside), connect the blacks to the neutral block on your light fitting (do not connect the black from the switched cable, mark this with red tape and connect it to the live block on your light fitting) connect all the earths to the earth block on your light fitting.

Fit light back to ceiling, turn power back on and test. As this was not wired incorrectly by yourself I would definitely suggest you get an electrician to check all your light fittings as there may be others which have been wired incorrectly where the neutral to the lamp is being switched and not the live (which is how it should always be wired, you must never put a switch on the neutral!)

PLEASE NOTE: All of the above advice is given based on what I can see in your picture, I accept no responsibility should it be incorrect, others here on the forum will soon correct any incorrect advice I may have given.

All the best
Dan

PS - Let us know how you get on.

 

[kevnurse]

I assume that the photo depicts exactly how you found the wires when you removed the previous lamp. If so, whoever wired in the original light appears to have done it slightly wrong. The original light appears to have been installed on the live side of the switch, such that the switch provided a neutral rather than a live supply to the filament.

All 3 of the red wires should be joined together. One of the red wires, together with its associated black wire will go to the switch. The associated black wire will become live whenever the switch is on and is known as a switched live wire. That black (switched live) wire should then connect only to the brown wire in the new lamp. The blue wire in the lamp should connect to the remaining 2 black wires. All 4 earths should connect together.

Although you might be correct in thinking that the cable associated with the wire at point C is the switch cable, you need to positively identify the switch cable before you do anything else. Using the multimeter, a simple DC circuit test, from point C to point D through the switch at the on position will suffice.

Hope this helps

 

[Steve]

Why is the red wire scorched? thats what i want to know.

and put some earth sleeving on the earths.

 

[breezer]

is there no connector blcok at D?

 

[RF Lighting]

Why is the red wire scorched? thats what i want to know.

and put some earth sleeving on the earths.

It was probably into one of those horrid old batten lampholders, or similar.

Anyway @OP you need to pull some spare on the cables and completely remove the burnt bits or wiring.