I've just replaced 5 33W G9 halogen bulbs in a light fitting with 1W G9 LED
As I swapped the bulbs one by one all seemed normal until I unplugged the
last halogen at which point the other four LEDs started glowing dimly.
Replacing the halogen bulb turned the LEDs off again.
Now with all five bulbs in they all continue to glow dimly when "off" and
work normally when on.
How do I fix this? It's a one-way switch that only controls one light. It
is next to a two-way one that controls the upstairs hall light.
(I've just replaced all the halogens with LEDs in the upstairs hall light
but it doesn't display this phenomenon.)
It will be a case of inductive coupling - when "off" the switched live
is left floating - its obviously getting enough voltage induced in it to
pass a very small current through the LEDs SMPSUs.
You need a small load near the lamp fitting to "pull down" the switched
live when off. IIRC TLC had a suitable widget, but I can't recall what
they called it to search their site. (a high value resistor, or even
suitably selected capacitor would probably add enough load to discharge
the floating wire)
Induction. If you want to stop it, replace the on/off switch with a
change-over switch with Common connected to the lamps and NO and NC to
live and neutral respectively. Then, in the 'off' position, both sides
of the lamps will be connected to neutral rather than having one side
floating. Careful how you document it, though, for anyone who may follow
Yes - one with 3 contacts, with either NO or NC being connected to COM.
I guess that's what a 2-way switch is(!) but I didn't call it that
because it wouldn't actually be used for conventional 2-way switching in
It would have to be a specific change over switch. A normal 2 way light
switch cannot be used as a changeover switch in the way you suggest. A
change over switch needs a "break before make" contact.
What often happens in your suggestion is that when the switch is operated
there is a small short of the NO and NC connection to COM as the terminals
are not designed to take such switching. This is something I have seen at
work several times. It works on paper but not in practice.
As an aside, the OP may not have a neutral at the back of light switch! Some
of us can still manage to wire a lighting circuit without a neutral at a
If you wanted to avoid wiring changes then using a miniature SPST mains
relay at the ceiling rose, with the coil across switched live and
neutral, and the main contacts between neutral and the lamp holder
neutral, you would achieve the same effect - i.e. disconnecting the
neutral from the lamp when the switched live is removed and the relay
(and to keep it really simple, you could probably skip wiring the
neutral through the relay - the load of the coil would likely stop the
glowing anyway ;-)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.