Just installed a new light at the bottom of the stairs ,this is connected to a 2 gang down stairs (1 feed to the light itself & 1 to outside light,upstairs it is connected to 3 gang switch (loft light upstairs light & downstairs light).
The switches were put in by a qualified sparks not my bag,the thing is if you turn downstairs light on downstairs you cannot turn it off upstairs also on position upstairs is off for the light downstairs to get the light to turn off you have to go down stairs,any help would be appreciated many thanks for reading this post.All other lights on the switches function normally.
Best Answer
That is simply a mis-wired 3-way.
On each switch you'll have a "common" terminal and two others. Typically a black screw and two gold. You need to confirm that the "travelers" are on the gold screws. Look at this diagram to see what I mean.
In this case the black/red pair are the travelers, but could be any colors depending on how it's wired. Just keep in mind, the same two wires must be on the travelers.