Old wiring - 3-way switches

[zeus_rw]

Made a boob, I was replacing lots of crusty old switches in my house (Canada 1950's - I assume the electricals are from new) and I seem to have messed up the 3-way switches (1 at top and 1 at bottom of stairs). The wiring as I said is old and does not seem to conform to any wiring diagrams I have found. Although the wire colours seem to be in line with some diagrams, I'm not confident that they are what they should be. Let me explain.

I have (at each switch box) one set of three wires (black, white and red) and one set of two wires (black and white). Inside both of the switch boxes the two white wires are connected together thus leaving the two black wires and the red wire. I'm not sure which way around to connect the wires to the switch. I have two gold screws and a black screw on each of the new 3-way switches (the black screw being the common) but cannot for the life of me figure out which way round the wires should be. Any ideas would be greatly appreciated. (Note - there are no earth wires - it's old wiring and I'm gradually adding earths as we update each room).

Help...

 

[plugwash]

the black wires from the two core cables go to the common terminals of the switches

the black and red wires from the three core cables go to the other terminals of the switches (doesn't matter which way round you put the red and black).

 

[zeus_rw]

the black wires from the two core cables go to the common terminals of the switches

the black and red wires from the three core cables go to the other terminals of the switches (doesn't matter which way round you put the red and black).

Thanks PW

I've tried that but to no avail... if "someone" had connected the new switch up incorrectly on "their" first attempt at replacing the old switch, could "they" have caused damage (to the wiring or the switch) that would mean a subsequent correct connection still wouldn't work?

Here's hoping!!!

 

[plugwash]

seems pretty unlikely if you never touched the white wires.

are you sure there isn't a tripped breaker or a blown fuse somewhere (possiblly hidden somewhere seperate from your fuse box)

another possibility is that the wire has broken inside the insulation. If this is the case depending on where the break is it may be possible to cut back and joint within the box.

give the inidividula wires a tug with pliers and see if they pull out of the insulation.

yet another posisbility is that the connection between the whites is dodgy

do you have a multimeter?