Intermediate switch wiring

[Charles R]

Can anyone give me a few clues please .    At the top of the stairs I have two intermediate switches facing each other .   The one on the left as I arrive at the top , works , but only when the switch opposite is in  one position .  I can operate the light with this switch fine ,on and off etc ,  but must always return it to that same position for the other lights to work .   If I forget to return this switch to that one position , my sister asks why the lights don’t work . Clearly the wiring is wrong somewhere .   I simply want to turn the lights on and off and not rely on keeping this one switch in the same position.   I could put one of those plastic locks you can buy on the switch to stop it being used and kept in one position , but would like to try wiring it correctly .

i am new to the forum and this is my first post .    I can post pictures or tell you where the wiring 

goes .    Both intermediate switches are Crabtree .     Both switches have two black and two grey wires in the terminals , with one switch live on one of the black wires .   All the other wires 

are in choc blocks .    I would be very grateful for any advice or clues you can give me .

 

[Murdoch]

Are you sure that they are both intermediate switches ?

 

[Doc Hudson]

Has it ever worked correctly, and/or has someone replaced any of the switches that control this light in the recent past? If it has never worked it is possible that has just never been connected correctly, or it may be that when originally wired someone forgot to put in adequate cables to allow full intermediate switching. To verify exactly where things should go, you do really need to test the continuity between the switches to identify exactly which wires go where.  Also you need a suitable voltage testing device so you can confirm where the supply live comes in and the switched live goes out to the lamp.  

The basic concept of intermediate switching is as per this image.



Doc H.

 

[Evans Electric]

Are you sure that they are both intermediate switches ?

As Murdo says ,  there are times when a switch is fitted to prevent the  sights from working  ,  quite rare but it happens .

More likely to be a wiring **** up  though .     Is it merely  that the stairs light can be switched on or off at any of  four switches ?  

 

[ProDave]

Sounds to me like one wire has fallen out of the back of the switch that now has to be left in a particular position.

 

[Charles R]

Has it ever worked correctly, and/or has someone replaced any of the switches that control this light in the recent past? If it has never worked it is possible that has just never been connected correctly, or it may be that when originally wired someone forgot to put in adequate cables to allow full intermediate switching. To verify exactly where things should go, you do really need to test the continuity between the switches to identify exactly which wires go where.  Also you need a suitable voltage testing device so you can confirm where the supply live comes in and the switched live goes out to the lamp.  

The basic concept of intermediate switching is as per this image.

View attachment 10493

Doc H.

Thanks Doc ,   On this diagram,  where is the switch live wire go .    The third one on the right on mind is another Crabtree intermediate switch like the middle one above and has two black , two grey and two red wires in a choc block .    I think the electrician who wired it , must have thought if you come out of the bedroom door to the landing , you have a light on your left to the landing .   This is fine , but if you leave it switched in the wrong position , the other lights don’t work .   When you switch a light on and off , you don’t then move to another switch ?    As I mention , I could just cover this switch set in the down position and all other lights will work .

 

[Charles R]

Thanks Pro Dave ,  all wires are in place , but probably wrong place .  If I press this switch on and off it works fine ,  but I cant leave the switch in the down position .

if I leave it off , the opposite light switch and bottom of stairs light don’t work .

it has to be set in this same position .   

 

[Charles R]

Yes Evans ,  but for the other lights to work normally , they depend on this one switch being in a set position.   This switch works fine but you have to remember leave it that set position , or the other lights won’t work 

 

[Murdoch]

Op , you could start by guessing at changes BUT make a note of how they are connected before you start or it’ll end up costing more to fix ....

 

[Sharpend]

When you say other lights, to what are you referring, the lights in bedrooms etc or additional landing/ hall lights? 

 

[Doc Hudson]

Thanks Doc ,   On this diagram,  where is the switch live wire go .    The third one on the right on mind is another Crabtree intermediate switch like the middle one above and has two black , two grey and two red wires in a choc block .    I think the electrician who wired it , must have thought if you come out of the bedroom door to the landing , you have a light on your left to the landing .   This is fine , but if you leave it switched in the wrong position , the other lights don’t work .   When you switch a light on and off , you don’t then move to another switch ?    As I mention , I could just cover this switch set in the down position and all other lights will work .

If you can't understand the concept of how intermediate switch wiring works from this drawing and how to apply it to your arrangement then you will probably need to employ someone who does understand. But I will ask again;  (1) Has it ever worked?  (2) have any of the switches been replaced recently?   Plus (3)  When did this electrician you mention last work on it? 

Please note there are several ways light switch wiring can be arranged to achieve the desired result. It is not possible for anyone over the internet to say the black wire goes in 'A' and the red wire goes in 'B'.   

Doc H.

 

[Charles R]

The electrician who installed it worked on it many years ago, it was a major build.  We don't live in the house, its a second home.       Its not something you notice at once because if that light switch is set one way , the actual switch, then all the lights at the bottom and on the landing work fine.    Yes I do understand the above diagram but mine has single pole at the bottom of the stairs,  then intermediate, on the landing at the top, then another intermediate switch a metre opposite before you enter a bedroom.    I can operate the lights fine with this switch, on and off.

And if I press the switch down I can operate the other switches to turn lights on and off.   BUT,   if I turn the switch up and try use the other switches  they don't work.  Only when the switch is pressed down do the other lights work.    Thanks anyway,  I will get someone in  to look at it.               

 

[Sharpend]

I wouldn’t be surprised if this switch was previously a 2gang switch which someone has tried to convert to an intermediate. 
am I right I’m thinking that this switch has two blacks, two greys, and an additional core? 

 

[Murdoch]

I wouldn’t be surprised if this switch was previously a 2gang switch which someone has tried to convert to an intermediate. 
am I right I’m thinking that this switch has two blacks, two greys, and an additional core? 

Thats a really good point.

OP how many switches do you have controlling the lights? 

 

[binky]

you're more likely to have this set-up than the above diagram

 

[Charles R]

Yes Murdoc,   Two blacks two greys.  And another core .    The other switch opposite,  two blacks two greys , and two reds .

in the middle one I have a red with the black switch live. Both wired same 

 

[Murdoch]

Yes Murdoc,   Two blacks two greys.  And another core .    The other switch opposite,  two blacks two greys , and two reds .

in the middle one I have a red with the black switch live. Both wired same 

How many switches in total?

 

[Charles R]

Hi murdoc  

four separate switches can work the lights 

downstairs,  at top, opposite , and outside a bathroom

at the top of the stairs bedroom,

opposite bedroom , turn right bathroom.  All have switches and can control landing lighting in some way

 

[Charles R]

These switches are outside the bedrooms and bathrooms, on the landing  .   

 

[binky]

so you have 2 intermediate switches on the landing?