2 switch light

[affleck]

i have an upstiars light which is controlled by 2 switches (one downstairs one upstairs) the problem is i can switch the light on with the one switch and switch it of with the other but for some reason i can't do it in reverse. any assistance please

 

[Qedelec]

Ben, theres no need to post twice, we read you the first time.

What did you do prior to this fault developing and can you supply information on how the two switches are wired. A pic would be nice.

 

[affleck]

sorry for the double post, i didn't think it had posted first time. I changed the upstairs switch only and placed the wires as they were. Someone else changed the light (red-red, black-black, earth-earth).

 

[affleck]

the switch i changed had one red (i put in common) and two black (i put in l1 and l2)

 

[Qedelec]

How is the other switch wired?
Have a look in the referrence section is has loads of examples.

 

[affleck]

the other switch is wired red - common. black - l1 and red and black - l2

 

[Qedelec]

So your saying the other switch has 4 wires, two red and two black?

 

[affleck]

yes

 

[affleck]

i am sorry about this, i will put all details in one query. I have two single switches, one downstairs and one upstairs to operate 1 light. If i flick the downstairs switch the light comes on and if i then flick the upstairs switch the light goes off (duh), but if i then go back downstairs and flick the switch nothing happens. The switches are wired as follows:

down stairs: 2 red & 2 black (1 red-com, 1black- l2, 1red/black-l3)
Upstairs: 1 red & 2 black (1 red-com, 1black-l2, 1black-l3)
The light 1 red, 1 black & 1 earth

The downstairs switch has not been changed, the upstairs switch has been changed from plastic to metal (i put the wires back in where they came out).

I am very appreciative of the assistance you guys have given in the past and any help again with this enquiry would be great.

 

[Qedelec]

You're gonne need a continuity meter to check this out, ..........but if you are adamant that you havent touched the downstairs switch, the only thing you could have done is tranposed the red and a black in the upstairs switch.

I have no idea why there are 4 wires in the downstairs switch.

 

[affleck]

thanks a lot, this might sound really thick but i assume by transposing you mean changing the red and black.

 

[Qedelec]

Yes but the trick is knowing which black.

 

[affleck]

what will happen if i just try the trial and error method

 

[pdcelec]

what will happen if i just try the trial and error method

You may fix the problem or you may kill yourself. Why not do it properly?

 

[affleck]

thanks for that, is there a way to tell which black?