electricallighting
i don't know much about light switches, but this is the first time i've encountered a 3 wired switch. All i know is 1 of them is a common. The problem is i don't know how to convert or wire the 3 wired switch to a new switch nowadays. See pics below
Old Switch
New Switch
I really don't have an idea how to wire them. The switch has 2 bulbs connected to it.
You say that, when you release the button, the contact opens again (resistance goes to infinity). But the light stays on, right? That means there must be some device which has a "memory" of the last action: you push a button, the light goes on and stays on, until you press the button again (or another button). I'm sure there is a device in the cabinet (Dutch: "schakelkast") which toggles its output on every pulse it receives, and which in this way controls the lamp.
The wire on the top right of the switch also hints in this direction; it's a signal wire, it's too thin to be a power wire. My hunch is that it carries the pulses to the actual switching device (I don't know what it's called).
Old UK wiring was as shown below
A comes from the fuse-box/consumer-unit (possibly via other junction-boxes/roses for other ceiling lights). B goes to the next ceiling light. C goes to the light switch for this lamp.
However most electricians will not have cable type C with two red wires and will have used regular cable with a black and a red wire and will put red tape around the end of the black wire to indicate it is "switched live" and not neutral (as it's black colour would suggest).
From what I've read, sometimes they would connect C's black wire to position 3 (the other red live wires) and then C's red wire would be the switched-live return from the switch. Connecting the black to the reds would make it obvious to an electrician and that might be why no wire had red-tape on it's end.
If someone has removed the red tape, you can:
A typical Non-Contact Voltage detector (NCV) and a typical mains tester
Finding which wires go to a switch using a multimeter (at least CatII 600V rated) on an isolated circuit (off at fusebox and tested for no 240V AC).
Looking at your photo, I think the top of the screw-block connections from left to right are probably:
In which case your lamp should be connected at the bottom of the two right-most positions.
Best Answer
In your old switch I expect the middle wire is the permanent live (hot) and the left and right wires each go to one of the two lamps. You can see that the left wire is not actually connected to the upper switch.
This is a system of wiring lights known as a "switch loop". In this system there are no neutral wires running to the switch.
You don't show any ground (earth) wires either, which would be very strange where I live but may be have been normal in the past where you live.
You can check which wire goes to which lamp by turning off the circuit breaker, checking the circuit is dead and then undoing the right wire. Make it safe by applying electricians tape or by inserting it into a loose wire-nut or terminal block. Then you can turn on the circuit breaker and see which one of the two lights no longer turns on.
The new switch should have come with connection instructions.
If not, I would use a continuity tester to find the common connections and the switched connections in the new switches before installing them.On closer inspection, I see there is a connection diagram moulded into the back of each switch
I would wire it like this:
Note that you need to cut the middle wire shorter and you need a new insulated piece of wire to connect the "common" terminals of the two switches
The new switches also have an insulation-trimming guide moulded on the back, which you should use if possible.
If the new switch is a smart-switch of some sort it probably needs a neutral connection. In that case you need to call an electrician to run new wires from a junction box to the switch. The electrician may need to make holes in your walls ceiling or floors which will need repairing and redecorating.