Fan isolator switch replacement (3 pole)

Hi all,

The switch popped off the other day, so picked up a replacement and rewired it (very difficult as no leeway with wires?!). I labelled the wires as I removed them, replaced like for like, but now the bathroom light only works when the fan is on. If I isolate, the light won't work. So obviously I have made a mistake. Photos are attached, and this is the current wiring:

N in 2: blue
N out: 1 grey
L2 in: 1 no sleeve
L2 out: 2, 1 brown 1 blue
L1 in: 2, 1 sleeve brown, 1 blue
L1 out:1 brown

I have an extractor fan with a timer, a single switch on the wall, and a basic 3 pole isolator switch.

Thought I'd done it without bothering you guys!

Thanks as always.

Martin.

you havent replaced like for like... you may have replaced colours like for like but some of them are in the wrong place. your going to need a multimeter at least to figure out which wire is which (and the aid of a drawing would help) then put it in the correct place

at a guess, id say its your brown in L2 out should be in L2 in but this is purely a guess. be warned if you want to try guessing then if tis wrong best case itll not work correctly (where you are now). worst case itll go bang and damage the light switch, your new switch or both

L2 out, 1 brown, 1 blue sounds wrong to me.  There should only be 1 wire in each OUT, and no electrician worth his salt would use blue as L without a very good reason and without sleeving it as brown.

I suspect that is not the only confusion

ProDave said:

L2 out, 1 brown, 1 blue sounds wrong to me.  There should only be 1 wire in each OUT, and no electrician worth his salt would use blue as L without a very good reason and without sleeving it as brown.

I suspect that is not the only confusion

Click to expand...

good point, looking again i suspect L2 and N out may also be crossed. also cant see any black which id ecpect for a 3 core going to the fan

Which one of the photos is the old switch BEFORE you touched anything?

Hi Dave, the top photo is the original, with some wires removed from the old plate.

Is it just the photo  or are those cables 2.5 ....does look a right mess. 

I think you need to go back to basics , get a multimeter  and buzz them all out . 

Strange to have a Bro & Bu  in L1 .   If theres a Grey  there should be  a Bro & Bk  to go with it .... which should be the fan wiring  .

The  functions of the fan cable  are  (1)  Permanent Live    (2)   Switched Live  (3)  Neutral .    That may help a bit .

If that's 1x 3Core&E  plus 2x Twin&Earth...

I would be thinking...

3Core & earth is on all of the 'Out' terminals  -> i.e. Out to fan & light

and the two Twin & earth connected to the 'In' terminals..   ->  Supply in and Switch in.

e.g.

L1 out  Brown of 3core

L2 out Black sleeved brown of 3 core

N out  Grey sleeved Blue of three core

L1 in  Both browns from 2x T&E

L2 in  Blue sleeved brown of switch cable T&E

N in  Blue of T&E supply cable

Plus all CPC's (earths) connected in terminal block/wago

Just need to meter them all out to verify assumptions are OK...

Guinness

They were a mess when I pulled them out, couldn't get access to them, so labelled them but obv made a mistake somewhere.

1 of the L1 ins is black, with a brown sleeve...

Martin.

Do you understand the concept of what functions the individual wires should be doing???

Without this basic knowledge I think you could be struggling...

e.g.

you will have a Supply / A light switch / A light / A fan switch / A fan

SUPPLY is just a Permanent Live, a Neutral & Earth  

LIGHT SWITCH needs a Permanent Live, a Switched Live & Earth 

THE LIGHT needs a Switched Live, a Neutral & Earth 

THE FAN needs a Permanent Live, a Switched Live, a Neutral & Earth

THE FAN SWITCH needs (a Permanent Live, a Switched Live, a Neutral & Earth) in and (a Permanent Live, a Switched Live, a Neutral & Earth) out.

its just a matter of connecting all of the common functions together on the correct sides of the appropriate switches....  :C

Are there just 3 cables  1x 3core&E  2x Twin&E ?

Guinness

A perfect example of why it's much better to take a 3 core from the light to the fan switch and another from there to the fan.

phil d said:

A perfect example of why it's much better to take a 3 core from the light to the fan switch and another from there to the fan.

Click to expand...

not really. youd have a join with loads of conenctions somewhere anyway, at least in the switch you can access them, unlike if they were tucked away in a loft somewhere, screwed to a jois, int he corner, then 20ft of insulation piled onto it

I would say a perfect example of loop at switch would be much better. That;s what i normally do, a 3 core out to the fan and a 2 core out to the light.

SPECIAL LOCATION said:

Do you understand the concept of what functions the individual wires should be doing???

Without this basic knowledge I think you could be struggling...

e.g.

you will have a Supply / A light switch / A light / A fan switch / A fan

SUPPLY is just a Permanent Live, a Neutral & Earth  

LIGHT SWITCH needs a Permanent Live, a Switched Live & Earth 

THE LIGHT needs a Switched Live, a Neutral & Earth 

THE FAN needs a Permanent Live, a Switched Live, a Neutral & Earth

THE FAN SWITCH needs (a Permanent Live, a Switched Live, a Neutral & Earth) in and (a Permanent Live, a Switched Live, a Neutral & Earth) out.

its just a matter of connecting all of the common functions together on the correct sides of the appropriate switches....  :C

Are there just 3 cables  1x 3core&E  2x Twin&E ?

Guinness

Click to expand...

Thanks Special,

Your last post was helpful too. I get the theory, I just find it difficult to tell what wire is what, how do I tell between a core&earth and a twin and earth? There is no flexibility and the wires won't put out any more so it's so awkward to get a better view. 

The fact that the light/fan/timer work only if on, but as soon as you turn isolator off (no fan) the light stops working does that mean that 1or 2 cables need to be switched? Or not that simple?

Martin.

Modern colours for twin and earth are Brown and blue, with a bare earth wire that gets sleeved with green and yellow sleeving.  3 core and earth colours are brown black and grey, again with the bare earth.

The browns are 'usually' permanent live, though that may not be the case , the blues can be neutral or live depending on how its been wired, same for the grey and the black. You really need to have some sort of meter to determine what's what. The only thing we can say for certain is that the earths 'should not' have been used for anything other than earth. Though if its been wired by a DIYer......

It's a relatively modern flat so i imagine electricians come in and do the jobs as quick as possible!

Couple of things that may help .

First , a multi meter can be purchased for £8 - £10   or get an old door bell , strap a battery  to it , wire so it rings when you touch the two wires together and use that . 

What may help is to open the fan up and make a note of how the 3 core is connected .   Fan terminals will be marked  either ...(L)  (S/L)  (N)     or  (P/L)   (S/L)  (N) 

Connect those colours  to your switch   (whatever colour you found at fan)    (L)  to  L1out            (S/L) to ( L2 out)      N to (N)  .

Have a look in the switch , hopefully theres just a    2core cable   (Bro & Bu)   & come back on here. 

Evans Electric said:

Couple of things that may help .

First , a multi meter can be purchased for £8 - £10   or get an old door bell , strap a battery  to it , wire so it rings when you touch the two wires together and use that . 

What may help is to open the fan up and make a note of how the 3 core is connected .   Fan terminals will be marked  either ...(L)  (S/L)  (N)     or  (P/L)   (S/L)  (N) 

Connect those colours  to your switch   (whatever colour you found at fan)    (L)  to  L1out            (S/L) to ( L2 out)      N to (N)  .

Have a look in the switch , hopefully theres just a    2core cable   (Bro & Bu)   & come back on here. 

Click to expand...

Great shout Ev, thank you.

I will have a look later tonight, the fan wiring is easy to access, I will also put a picture up.

Regards,

Martin.

Can I suggest you open the isolator. It sounds as though the light feed has been taken from the isolator but put on the wrong side.  

You may find a 3core &earth at light switch with just a twin and earth and in the fan isolator two three cores and a twin. 

Here is a photo of the fan wiring.

I am not able to look at wiring tonight as j have to go back out, but will look asap!