Help please. Changing old 2 way single gang switch to new

Discussion in 'Electricians' Talk' started by sally green, Oct 17, 2021.

  1. sally green

    sally green Active Member

    Hey
    I bought a 2 way light switch for the stairs recently.
    Next door guy kindly changed all of the single way switches like for like no problem.

    The problem with the 2 way is and its old wiring, black and red upstairs and from below is a newer versions, red, blue and yellow.

    The wiring was fitted to the old switch as follows

    2 reds into one hole at the top where is is only one hole on the switch.
    Black and blue fitted to the bottom in one hole
    The yellow fitted to the bottom, second hole in one hole again

    The new switch has 'com' written on it and the guy fitted the two reds in there. He fitted the black and blue into the btoom hole. Next to that hole he fitted the yellow.

    There is no earth connection on the new MK switch plastic type. Nor is there an erath in the the cutout box fitted to the wall ie the one the light plate fits to.

    As a result the lights turn on/off one switch

    Thanks
     
  2. Bazza

    Bazza Screwfix Select

    I’m afraid we need a picture of the wiring to the old switch (when it was working) and a pic of the new switch.
    There’s no standard layout or ways of marking them.

    if you don’t have then it’s phone a sparky time…
     
    tore81 likes this.
  3. sally green

    sally green Active Member

    Ok thanks
    Not great with pics
    The old switch is a snap fit pics taken as fitted to wall missing top cover for pic purposes.

    The new socket a MK 2 way, one gang as is the old switch.
    I've drawn in colours the 2 red wires into the COM hole.
    Then you have the blue and the black in one hole and the yellow in the
    other hole. The man did put the yellow in the other hole and the black/blue in
    place of the yellow

    Light would only turn on and off at one switch when he tried the new switch.

    Thanks AA1.png
     

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  4. bright_Spark

    bright_Spark Screwfix Select

    Only one red wire should be in the common in both of the switches and at the other switch two wires in each of the bottom ones. Looks like he has got the common wire mixed up. You should have another red with the yellow. He needs to split the two reds in the common, put one of them in with the yellow and leave the other red in the common, if this doesnt work then swap the reds over for the other, it will work then.
     
  5. sally green

    sally green Active Member

    the new switch was not working when the wires were put in as per second picture, it was only switching on and off from one switch. It it is th white switch with wores draw on it and explanation given
     
  6. sally green

    sally green Active Member

    Red with yellow but yellow is live. The old switch works perfectly since we've been in this house, ie two red at top, blue and black together and then the yellow earth in the other hole
     
  7. bright_Spark

    bright_Spark Screwfix Select

    You are mising the strappers, a two way switch works with strappers inbetween the perm live and the other red is a switch wire. you ony have one strapper and why only 1 switch works.
     
  8. sparky steve

    sparky steve Screwfix Select

    CE108952-1910-4EF9-A6EB-2EEC25FA0711.jpeg 2way switching, the red, yellow & blue between the 2switches are known as the strapping wires.
     
  9. sally green

    sally green Active Member

    but why is it working with the old switch please, ie same layout
     
  10. sally green

    sally green Active Member

    Just to be clear, the lights are workinng fine with the exisiting old light switch why is that
     
  11. bright_Spark

    bright_Spark Screwfix Select

    If it is working fine then leave it alone.
     
  12. terrymac

    terrymac Screwfix Select

    Do both old switches turn light on and off ?
     
  13. Hell68

    Hell68 Active Member

    You say the new switch has com on it and I presume L1 and L2?
    Did the old switch have L1 L2 and L3?

    Might it be wired up incorrectly?

    Old L1 is now com
    Old L2 is L1
    And old L3 is L2
     

    Attached Files:

  14. sally green

    sally green Active Member

    just the one, when he changed the yelow to the other hole and blue and black to the other then the other switch turned it on and off but not both
     
  15. sally green

    sally green Active Member

    thanks - old switch has one hole at top and two at bottom.

    FYI, the one way light switches the guy changed only had two holes, ie one at top other at bottom - there switches are otherwise the same era, ie snap fit lid like in picture.


    What you are saying is making some sense to me i will show the man next door this thread tomorrow
     
  16. terrymac

    terrymac Screwfix Select

    Doesn't answer my question. Did both ORIGINAL switches turn the light on and off ,or didn't they ???
     
  17. bright_Spark

    bright_Spark Screwfix Select

    easiest way to explain a common 2 way lighting circuit. image.png
     
  18. sally green

    sally green Active Member

    The did and still do
     
  19. sally green

    sally green Active Member

    There is no earhting point on the new plastic switch or the plastic back box the switch fits on to - i have stated this earlier.

    The system as it is works, on/off as a working two way sytem
     
  20. terrymac

    terrymac Screwfix Select

    Thanks. The new switch isn't wired correctly then. The earth conductors can go together in an insulated terminal block ,that sits loosely inside the enclosure.
    Refer to bright sparks diagram for correct wiring info.
     

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