Author Topic: Curious CFL phenomenon  (Read 316 times)


  • Dez's butler
    • Musings of a Gentleman Cyclist
Curious CFL phenomenon
« on: November 27, 2017, 12:00:30 am »
Jan and I have noticed that after we turn the bedroom light out (no sniggering!) the CFL "bulb" still continued to flicker slightly. I am aware that they can glow faintly for a while afterwards, but this is different. Periodically a very faint flicker can be seen in one of the "arms" of the tube. How long this persists after we have turned the light out I don't know. It's not strong enough to light up the room, but is easily visible when you look straight at the light.

We have a perfectly ordinary old-fashioned switch with no fancy dimming or other capability.

Has anyone else seen this? What can be causing it?
You won. Get over it.


  • An appetite for the epic, but no real stamina
Re: Curious CFL phenomenon
« Reply #1 on: November 27, 2017, 12:15:44 am »
Capacitive coupling (or similar electromagnetic voodoo) inducing a voltage on the wiring downstream of the switch, with just enough oomph behind it to make the CFL electronics sort of start working a bit.  The next stage of this phenomenon is full-brightness flickers at random infrequent intervals, classically observed with an electronic (timer, motion/light sensor, whatever) or illuminated switch that leaks a bit of current through the load when off in order to power itself (because in the UK there isn't usually a neutral wire available at light switch positions).

It *might* be symptomatic of a wiring fault, but is probably harmless.
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Re: Curious CFL phenomenon
« Reply #2 on: November 27, 2017, 09:30:25 am »
Try a different lamp it could be a dodgy capacitor.
'Absence of evidence is not evidence of absence'.

Martin John Rees.