Replace 2 gang 2 way switch: 3 X 3 terminals vs 2 X 4

[chris1982]

I bought to a new 2 gang 2 way switch to replace an old one. To my surprise I just noticed that the current switch has 3 terminals at the top and 3 at the bottom. It is a made by MK, and probably 25 years old. But the switch I bought has 2 terminals on one side (com) and 4 on the other side (L*). One light is the for the kitchen, the other one for the outside.
In general, can I use this switch to replace the other one?
I haven't been able to look at where exactly each wire goes, but will do so later. I just skimmed around the box, so need to wait for the plaster to dry. I will post the exact wiring later, unless you tell me before that it is hopeless.
There are two switches for each of the two lights, and three cables at the back box. One cable seems to be reinforced, so probably is the one for the outside light. I don't know whether it goes to the light or to the other switch operating the outdoor light, which is directly on the other side of the outside wall. (Is there such a thing as a 1 gang intermediate and 1 gang normal 2 way switch on one plate?)

 

[Taylortwocities]

Take photos of both switches before you disconnect anything.

Look at the switches, they are laid out as two separate halves.
IIRC, the old MK ones are like this (ignore the S3 terminals in my picture)

Untitled

• Taylortwocities
• 29 Apr 2014
• 1

Your new one may be like the one on the right

 

[chris1982]

Hello. Thanks. The new one I have does look the one you have drawn. I will check whether the labels on the old one (when the plaster is dry). If the labels are the same on the new and the old switch, is it simply connecting the wires to the terminals with the same name (irrespective of their location)?
Of course I will take a note of what goes where. It is rather tight in the box, so I am not sure a photo will show everything, but I will take a few just in case.
Is there any point looking at the other two switches operating these lights?

 

[chris1982]

I had another look at the switch (and unfortunately wacked out a corner of plaster that wasn't fully dry yet... ), and you are right. It's simply divided up differently. The old one diagonally, the new one vertically where the commons are at the top and all the lives on the other side. Thanks a lot for that.
The only other difference between the switches is that the new one labels terminals as common, "1 way" and "2 way". So I take you use "1 way" the way L1 was wired, and "2 way" as L2?
Now it's getting dark, so I will only swap the switches only next weekend!

P.S.: I did look at the other (chrome) switch controlling that light, and found that it wasn't earthed! Luckily I had kept some old cable and connector block and sorted that out right away...

 

[ban-all-sheds]

Your new one may be like the one on the right

POP, surely, to use one's multimeter to work out which terminals are which?

 

[chris1982]

On the old switch there is actually a diagonal line drawn that is just in line with taylortwocities's conjecture. Also, on the side of the switch that operates the outdoor light, there is on that side of the diagonal line on COM, on L1 and on L2, which all take cores from the cable that runs outside: red to COM, blue and yellow to L1 and L2 (and an earth to the backbox). So that looks like bog standard two way switch.
On the other gang, there are two cables, one 3 core and one 2 core (both plus earth), and on the other switch there is the (or a, but the switches are working, so I'd think it is the same) 3 core cable as well. So again, looks like standard two way switching.
I do have a multimeter somewhere, but what would you recommend I measure? Continuity of the switch wires?

 

[chris1982]

Or did you mean to measure the new switch?

 

[EFLImpudence]

On the old switch there is actually a diagonal line drawn that is just in line with taylortwocities's conjecture.

It wasn't conjecture.

I do have a multimeter somewhere, but what would you recommend I measure? Continuity of the switch wires?

I think the suggestion was that you could have worked out which terminals did what.

 

[Taylortwocities]

You should not need to test anything.
Work out the transitions.

The old switch is marked
com, l1 and l2.
From what you say, so is the new switch.

 

[ban-all-sheds]

I think the suggestion was that you could have worked out which terminals did what.

 

[chris1982]

I swap the switches around and it worked like you guys said. Thanks.