Wiring for 2x 2 Gang 2 Way switches

[diypaul1982]

I have two 2 gang switches, one at the bottom of the stairs and one at the top of the stairs. At the bottom one switches the light on at the bottom of the stairs and one the light at the top of the stairs. At teh top of the stairs one swicthes the light for the top of the stairs and the other the bathroom light.

At the top of the stairs I have five wires, a blue and a brown from one of the grey cable and a blue and two brown from another grey cable.

At the bottom of the stairs I have four wires, black and red coming from one grey cable and two red coming from the other grey cable. I also have a small piece of (red) wire that is totally loose.

Could anyone suggest how I should wire up the two switches? I have looked at teh sticky post but could not find anything with a similair combination of wires. Any help much appreciated thanks.

 

[Steve]

How was it wired before?

You're going to need to find the other ends of these cables if you dont remember. You really should have written it all down.

If you have a multimeter it might be useful here.

One thing that concerns me is that no such cable exists with 2 brown and a blue core. Take a closer look at it. Does it have an earth core? Does one core look slightly smaller?

 

[diypaul1982]

It was a friend that unwired it and tried fitting the new one but some confusion over the labelling of the connections (L1, L2, L3 on the new, but L1, L2 Com on the old) led him to changing the wires around and forgetting the original configuration.

There is an earth on the wire with 2 brown and 1 blue and an earth on the wire with 1 black and 1 red.

I can't really trace the wires back as they in the plastered walls. I know that one brown wire is live upstairs and the red wire (one paired with the black) is live downstairs.

Any more ideas?

Also what is the function of the small indepentent wire that was does not come from the wall but was wired in previously?

Your help is much appreciated.

 

[Steve]

Its odd because there's no link between the switches. Otherwise I would normally be able to do this in a flash. All the wires upstairs are in new colours and all of downstairs is in old colours.

Phone your "friend" and ask him to buy you a cheap multimeter. <£10

This is the only way you'll be able to diagnose this.

If you can find any permenant live wires this will be a start. If you have a neon screwdriver this might do for this purpose.

The link wire carries the live from the downstairs switch feed to the second switch. You do NEED this wire.

 

[diypaul1982]

Thanks for the help so far. I will get a multimeter but could you explain how exactly would I use the link wire in the setup?

Most grateful

 

[Steve]

By connecting it between 2 terminals in your switch! Normally between the 2 COMs, but this varies as COM is not always used for permenant live.

 

[diypaul1982]

When I get the multimeter what will I have to do toy work out which wires go where?

Cheers

 

[Steve]

When I get the multimeter what will I have to do toy work out which wires go where?

Cheers

First you need to find the permenant lives. To do this terminate the wires into terminal blocks. Turn on the power. Test each core for 240 volts AC~ by putting the red probe on it, and the black probe to earth (the backbox).

When you have the lives, mark them with tape or something so you know.

What you could also do it take a digital photo of the switch wiring and post it to this forum. This might make things easier, as there could be something you haven't spotted, which an electrician could spot right away. If taking close up photos use macro focus so they aint blurry.

Also open up the landing light, bathroom light and hallway light and note what colours come from what wires and what each core is connected to. Again photos would help immensely.

See here to see how to host a picture.

 

[diypaul1982]

Back of the switch (Both are same)

The upstairs wiring (for bathroom and top of stairs lights). The live is the brown wire on the right.

The downstairs wiring (for downstairs and top of stairs lights). The live is the red wire on the right.

I have not been able to take the photos of the lights yet. Will you be able to help with the info here or will I need to get the pictures of the light fittings as well?

Your help is very much appreciated.

 

[MANDATE]

regarding your downstairs switches, they are both 2 way switches even though one of them is inverted.
One of the above is being used in a 2 way system, whilst the other is being used in a 1 way mode.
switch used in 1 way mode.
I would suggest the 'live' red and the black are the switch wires for your light at the bottom of stairs. You can prove this easily, put red into com and black into L1 and operate switch. (ignore L2)
switch used in 2 way mode.
If you study how 2 way switching works, you'll find two different methods of wiring. one method uses a strapper cable between the two 2 way switches comprising 3 core cable and an earlier method uses 2 core cable.
I would suggest your 2 red wires are the strapper wires.
In this older method you have a 'live' going into 'com' and the strapper wires coming from L1 and L2. At the other end of the 2 way system it is a mirror image. The strapper wires go into L1 and L2 and the wire coming from 'com' ( 'switched live') goes to the lamps, after the lamps the wire is called neutral.
In your set up, a 'live' wire was needed to go into 'com' and you can see the first switch has a live terminal so the short red wire would go 'com' to 'com' so both 'coms' are always live.

Upstairs you have almost the same situation, but this time you don't require to obtain another 'live' so no short red wire.
I would suggest the 'live' brown and the other from the same cable are related to the bathroom lamp, so again one switch is used in 1 way mode. So 'live' to 'com' other wire to L1. You can test this easily.
Now you should have three wires left. 2 should be the 'reds' from first switch and 1 should be 'switched live' going to lamps.
Problem here is you have three wires but colours don't match.
But again easy to test. with these wires each in separate terminal block for safety and the downstairs switch wired as stated and power on, one of the red strapper wires is live and must be connected to one of your 3 unknown wires which will also be live. flick the switch and a different wire will become live. So identfying the 2 strapper wires for L1 and L2 it matters not which one goes in L1. The remaining wire must be the 'switched live' thats goes into 'com'
I suggest you test this in stages. ie perhaps the bathroom lamp followed by the downstairs lamp without the short red wire and then finally fit the short red and complete test.

 

[Steve]

Here goes nothing . . .

At the top switch, that blue wire goes into a seperate grey sheath It aint the same cable. That is why I was a trifle confused.

I need you to do one more test for me.

Connect (with the power OFF) the blue and brown together in the bottom of the upstairs switch. Go downstairs and test for continuity (resistance, ohms) between the double red cores on the left. You should find continuity, very low resistance. Go and disconnect them upstairs and test for continuity again downstairs. You should find no continuity. If this is the case, they are one cable joined together somewhere and you can go ahead and . . .

Upstairs:

Switch one - double brown wire, one brown to COM, one brown to L1.
switch two - blue and brown from bottom to L1 and L2. Single blue to COM.

Downstairs:

Switch one - red and black on the right, red to L1 black to COM.
Switch two - double red to L1 and L2. Link wire from COM to L1 of switch one.

If this doesn't work I'll eat my proverbial hat.

 

[diypaul1982]

That has worked a treat. You are genius!

All your help has been greatly appreciated.

Thank you very much.

 

[Steve]

Phew my hat was quaking