2 way switch problem

[djp22]

Hi I have a switch problem that has been going on for years and would now like to resolve.Have sometimes to go down stairs and alter the switch for the upstairs to work.
1 Single Gang 2 way switch upstairs has a Red & Black Cable into it from a junction box in the loft.
Also a seperate red that goes to the lamp and switch the other wire from the lamp a black goes to junction box.
The junction box has 3 terminals 1 which has black wires 1 which has red and the final one earth cables
Downstairs there is a 2 gang 2 way switch A red & black cable goes to the right hand switch (com & L1) and operates the downstairs light.We also have a jump wire from the red cable of the downstairs light switch and a red and black to go to the other switch to operate upstairs light.
I seem to have tried all sorts of combinations without the switches operating properley.
I did remove the fuse and wires from both switches put the fuse back and touch tested the wires to find that the only live was the downstairs jump wire.
Sorry if that was a bit long but have tried to explain layout as well as possible and would be very grateful for any recommendation as to what goes where as pensioners we need to be able to see coming down in the middle of the night.Many thanks

 

[regsmyth]

Well I've tried to work out what the problem is but your description is a little confusing.
However, presumably the jump wire in the downstairs switch goes to the COM terminal.
If so, the red and black in that switch from the cable that goes to the other switch should be in L1 and L2 (doesn't matter which way round).
This same cable in the other switch should have it's red and black also into L1 and L2.
The red wire that goes from the upstairs switch to the lamp should be in the COM terminal.
But I don't understand what the red and black cable from the junction box are doing in the upstairs switch. If my understanding is correct, they shouldn't be needed.
Presumably the junction box in the loft contains permanent live, neutral and earth.

 

[securespark]

Yeah, reg is making sense.

From what you're saying, the JB contains only permanent live, neutral & earth (the switched live for the landing coming direct from the top landing switch).

So, I think you must be mistaken that the red/black from the switch goes to the JB. I think (as it normally does) that it links directly to the switch downstairs.

You can check this with a multimeter (tenner from Maplin) set to continuity.

WITH THE POWER OFF, short the red/black on the landing switch downstairs together then put the meter across the red black on L1 L2 upstairs and you should get a buzz or a reading on the display if it is continuous.

So, the single red in the common & the red black in L1/L2 upstairs is OK.

There are two cables in the downstairs switch. One is (presumably) for the hall light. The link is to provide a feed across from one common terminal to the other to power the landing light.

The reason you get the fault you describe is either because of a loose connection on an L1 or L2 terminal or one of the L1 or L2 wires has snapped off or, more rarely, the switch mechanism is kaput.

But investing a tenner in a multimeter will pay dividends. Even if you never use it again (unlikely), it will have paid for itself and you will have learnt a great deal.

Go forth and sort it out!

 

[ericmark]

I could not really work out what you have from description but I can guess what the problem is.

Years ago it was common to run just two wires between the switches. Today we use three. What they did was borrow a line from another light. Often using two gang switches so they took line from switch next to the two way one.

However this method produced mains hum on radios and as we started to use more power for our lights we would often split the circuits using a different feed for upstairs and down stairs. This then resulted in what's called a borrowed neutral although really it's the line that's borrowed.

When we started using RCD's the borrowed neutral would trip the RCD so electricians had to do something. They have a number of options but one of those is to disconnect the borrowed supply.

That would cause what you describe.

So in real terms you have two options.
1) Run a new three core cable between the switches.
2) Use a wireless connection.

These people make wireless options as do a few more. This advert shows how the unit fits behind a standard switch. They may need a deeper box to take it all.

However what ever method you use first you need to draw out what you have and that means a multi-meter or some other method to bell out the wires. As the name suggests something which makes a sound is easy way. Battery operated door bell for example.

Also with two way switching the method taught at school does not work as it requires a junction block in the switch. We use this diagram.