Any idea what's going on here?

[hellboy]

Hi All,

I've been installing a new shower and have come to the extractor fan. When I removed the old one, I think some wires disconnected which prevented me from taking photos.

- The fan has an on/off switch outside the bathroom
- The flat twin cable is live when tested with an electrical screwdriver and is on the light circuit. There doesn't seem to be any power coming from the other.
- The fan is a timer model

Can anyone give an idea of what the wires, where they go and how best to determine what they are?

I've got an electricians screwdriver and multi-meter.

Thanks for the help guys. Fully aware not to mess with electrics so I'll only go ahead if it seems safe to do so. I've taken care to isolate the circuit when working around it.

 

[chivers67]

The Other Cable is for the switch or light then? You can test it for voltage and if none present test for resistance to confirm this by switching the switch or taking the lamp out?.

 

[mattylad]

If your referring to one of those little screwdrivers with a neon lamp in it then NO you have not got an electricians screwdriver as they will not use them, remove the neon, don't ever use it to see if there is any voltage. search and you will find out why.

As for where the wires go, the batteries in my crystal ball are flat right now.

The flat twin wire, what colour are both cores?
That may be the permanent lighting supply from the lighting circuit.

is there 1 or 2 wires in the terminal block?
The other cable may be the switched live from the light switch, does it become live when the bathroom light is turned on? You can test that using the multimeter set to 250vAC, probes in the volt positions and black to earth, red to the other wire.

 

[chivers67]

https://www.diynot.com/wiki/Electrics:fan

 

[hellboy]

Thanks fellas.

I’ve dumped the screwdriver!

- the flat twin- both cores are brown.
- 1 wire into the terminal block From the 3 core
- I get a reading of 260v on the longer of the 2 brown cores in the flat twin. Voltage is only present when the isolating switch is up.

I DONT seem to get a voltage reading from the 3 core cable.

 

[hellboy]

Hey fellas, any ideas?

By looking at the wires is it possible that the live from the twin core, goes into the terminal block?

 

[terryplumb]

You need to put each conductor into seperate terminal blocks ,then use your multimeter to establish if there is a permanent live, which conductor is the switched live, and which is the neutral.

 

[SUNRAY]

Before I can offer any advice I would like more information:

Is the fan operated by the bathroom light switch? Did it run on after the light is off?
Is the 'on off switch outside the bathroom' the light switch or another one? does it have a wide button?

Please... with the power off put the wires into a piece of choc block for safety and take a great deal of care when taking these readings.
what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched off?
what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched on?

More questions may follow

 

[ericmark]

I agree with @SUNRAY first step is put all wires into choc block, I also agree the neon screwdriver has its uses, but since @EFLImpudence has pointed out I would not expand unless you ask. This was my wiring diagram

what you need to do is build your own, so on the choc block label the wires 1,2,3 etc then print or draw a diagram saying what each wire is as you find out, in the main there are two methods with fault finding, one is guess, and the other is test, guess may work some times, but your at the test stage.

 

[hellboy]

Thanks for the responses!

Before I can offer any advice I would like more information:

Is the fan operated by the bathroom light switch? Did it run on after the light is off? - Sorry, don't know, not lived here for 4 years and can't be sure.
Is the 'on off switch outside the bathroom' the light switch or another one? does it have a wide button? - Basic narrow light type switch. I've removed face and it has 4 terminals and an earth point. Has a 2 core flat twin cable from each side from, only 1 core is connected.

Please... with the power off put the wires into a piece of choc block for safety and take a great deal of care when taking these readings. Assuming once in a choc block I'm to turn the power back on for testing?
what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched off?
what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched on?

More questions may follow
View attachment 197962

 

[SUNRAY]

I'm assuming the picture so far is the fan position, is the light still in place and working?

Thanks for the responses!
Is the 'on off switch outside the bathroom' the light switch or another one? does it have a wide button? - Basic narrow light type switch. I've removed face and it has 4 terminals and an earth point. Has a 2 core flat twin cable from each side from, only 1 core is connected.

Is this the light switch? or are there 2 switches?
Is the earth wire connected?

Can you post pictures of the light fitting wiring and the switch wiring please? and if you haven't thrown it away yet the electricians screwdriver too.

Thanks for the responses!Please... with the power off put the wires into a piece of choc block for safety and take a great deal of care when taking these readings. Assuming once in a choc block I'm to turn the power back on for testing?

Yes, make the ends of the wires safe in conectcor block so there is no chance of them touching anything if they move [but you can still test them with your multimeter] then turn power back on.


what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched off?
what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched on?

 

[hellboy]

Cant find screwdriver. Its has a little lamp, bought from big DIY store.

 

[hellboy]

Before I can offer any advice I would like more information:



what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched off?
what voltages are present between neutral [blue wire] and points 1, 2 & 3 with the light switched on?


View attachment 197962

Light dimmer switch on - 1 - 0V / 2 - 266V / 3 - 0V

Light dimmer off - 1 - 0V / 2 - 266V / 3 - 0V

Fan switch off - zero readings on any cable

Fan switch on - 266V on cable 2 only

The voltage from cable 2 flys around upto 700, then stabilises once good connection to multimeter.

Also, my mistake. The flat twin which I said had only 2 wires, actually has 2 brown and a bare wire.

Thanks again guys, very much appreciated.

 

[hellboy]

Please start another thread to discuss test equipment. A few people have been really helpful and are guiding me through a process, hijacking the thread will likely have people lose interest.

//edited

see https://www.diynot.com/diy/threads/electric-voltage-probe-with-indicator-lights.548468/#post-4677643

 

[securespark]

2 looks like a permanent live that comes from the switched side (if you see what I mean) of the fan iso.

With the fan switch on and the light on, you should get a live that goes off when the light does.