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The setup:

I have a 2 gang touch sensitive switch which has a live feed coming into it from mains light circuit, which also goes on to feed the switch above too (same 2 gang touch sensitive switch but dimmable).

Connected to the 1st gang of the initial switch is the live wire for the outside lights (3x 6W LEDs) which works fine. Connected to the 2nd is the live wire for the plinth lights (20x 2W LEDs) which causes a problem. All the neutral wires are bundled together (4 of them - feed from main light circuit, feed to 2nd dimmable switch, outside lights, plinth lights).

The plinth circuit switch just turns the power on/off to another mechanical switch under the worktop which the plinth LEDs are always plugged into.

The problem:

With both the touch switch and mechanical switch off, the LEDs are off.

When we turn the mechanical switch on, LEDs stay off.

When we then turn the touch switch on the LEDs come on.

But when we turn the touch switch off, the LEDs flash every few seconds (building up current in capacitor somewhere and releasing periodically).

Even with the touch switch turned off, there seems to be 150V hanging around at both the mechanical switch terminals and the touch switch live wire (only plinth circuit).

Attempted solutions:

We switched the outside lights and plinth lights live wires to the opposite switch gangs, the 150V seemed to follow the plinth live wire and the outside lights worked fine still, so there doesn’t seem to be problem with the switch (as first sight).

We added a suppressor circuit (just an LCR circuit from maplin we read somewhere tends to fix LEDs flashing due to induced current), but it just added another capacitor to the circuit and it flashes twice - at different brightnesses. (We added this to both the mechanical switch end and the touch switch end, both same results).

We wired the exact same circuit to another mechanical 2 gang switch instead of the touch switch and now everything is working fine... So maybe there is something wrong with the touch switch?

We read somewhere about adding a fluorescent bulb to the circuit to draw the excess current and stop charging the capacitors bur that seems like a silly work around.

We had an idea of adding just a resistor to get the same solution as above, or maybe a relay instead?

Does anyone have any ideas of what could be going wrong with the touch switch or possibly with the plinth lights circuit itself? Or possibly any solutions anyone can think of?

At this point we've fixed it by just using a mechanical switch but it's bugging us as to why the 150V is leaking and why it is following that particular circuit, we'd like to use the touch switch to match the dimmable switch.

Any help in ideas much appreciated.

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I'm guessing your switch does not have a dedicated neutral connection. The switch needs power in order for the touch sensor to operate. Without a dedicated neutral, it acts as a high-resistance device and leaks power back over the other hot connector. With incandescent bulbs, there is not enough power to light them up and you don't notice this, but with LED and fluorescent bulbs, the voltage leak is enough to power them partially. The flashing is due to the ballast.

The only way to resolve this is to either use incandescent bulbs or replace the switch with a model that has a dedicated neutral connection -- assuming your electrical box where the switch is also has a neutral available.

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