flickering CFL?

[Stephen]

Hello,

The cfl in the bathroom light has started flickering when switched off. I'll get the step ladder out later and replace the bulb and see what happens. There has been no changes to the wiring, so that cannot be the cause.

The light is operated by a cord switch and at first I thought may be the switch was faulty and passing a small current but I now think it might be a bulb problem. When the light is switched off it flashes every few seconds but left for a few hours, the flashing seems to stop. If the switch was passing a small current, the flashing ought to be continuous.

Do cfls have a capacitor? I'm wondering whether something charges up when the light is on and then gradually discharges, causing the flashes, when the light is switched off. After some time whatever it is "flat" and so the flashing stops. Would that make sense?

Thanks, Stephen.

[Andy Burns]

It's a well known effect, there *is* a capacitor that can slowly charge from induced current from nearby wires, and then give a flash as it eventually reaches sufficient level to briefly drive the lamp.

You say no wiring changes, but perhaps you've replaced a nearby incandescent lamp with another CFL, and where previously the induced current was going un-noticed into that filament, it's now "easier" for it to flash the bathroom CFL? Or maybe you've left a nearby 2, or 3 way switched lighting circuit in a combination you don't usually?

[Brian Gaff]

These weird effects seem to be quite common according to friends of mine, even a nearby thunder storm seems to do this sort of thing, presumably by induced current charging up a capacitor. I'd have thought these lamps or fittings ought to have a very high resistance resistor across any capacitor to stop it. Brian

[meow2222]

NT

[Michael Chare]

I have one that I know flashes when switched off. I have replaced it with an LED bulb, now that 1000 lumen ones can be bought for less than a tenner.

[Stephen]

Thanks for all the replies; they have been very interesting.

It seemed curious to me that the flashes only occurred at night. I wondered if perhaps they were happening all the time but were less visible during the day. However I don't think that is the case. I did wonder whether like one reply said, it is dependant on another circuit being in a certain state nearby, so perhaps it only happens when another light nearby is switched on?

However this morning it occurred to me that there is a fan over the shower which is switched by the light. The fan has an isolator and SWMBO switches off the isolator and only switches it on when she has a shower, so possibly there is something amiss with the fan and it is passing current from its permanent live to the switched live which is causing the flashes. I will investigate more.

Thanks, Stephen.