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Electrical

Why is electricity SWITCHING from the live wire to the switch live wire when I turn on the light?

Anonymous user 15/03/2024 - 2.33 PM

I just attempted to replace my bathroom extractor fan as the previous one seemed to have died, but the new one does not work either, which makes me wonder what the issue really is. The previous one had a timer overrun feature and so does the replacement. I was very careful to ensure that the brown live (L) wire, the grey live switch (LS) wire and the black neutral (N) wire were documented from the existing before disconnecting it, and then careful to ensure that I wired to replacement unit appropriately. But it does not work either. My multimeter indicates that when the bathroom light is OFF, the L wire registers 250V, and the LS registers none. That makes sense. And when the bathroom light is turned ON, the LS wire registers 250V, but the L wire now registers none. That is, the current has swapped from the L to LS wires somehow, and therefore the L is not behaving as a permanent live. How can this be? If I cannot resolve this with this new model, I'm thinking I'll just buy another new fan without a timer, and connect it to the LS and N wires, and just cap/seal off the L wire. Any reason this solution might fail?

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4 Answers

DEACON ELECTRICAL SERVICES

Rating: 5 out of 5
Grimsby
I think there is something very wrong with your set up and I would recommend an electrician to attend and sort it.
Answered29 January 2017
1

D.A.K Electrical

Rating: 5 out of 5
Trowbridge
This could be a polarity issue which may cause alsorts of problems with the fan if its been DIY installed originally. The colours you've mentioned aren't connected in the order many modern day electricians do, so i'd take a stab at this being the issue.
Answered29 January 2017
0

Excelsior Engineering

Rating: 5 out of 5
Merthyr Tydfil
Where does the 3-core cable in the fan come from? Check it's going to the light fitting and not to the switch or a JB. Lee
Answered31 January 2017
0

Anonymous user

In a 3 core cable Black is not N it should be L2 (or switched live) gray is N. Cables should be marked with an ID brown for L, blue for N. But this is not done all the time, so you should check your assumptions that the colour of wires is as you think it should be. You should check what the wires are connected to at each end it could be they have been connected differently either in the isolator or in the light fitting.
Answered31 July 2020
0