Flickering lightbulb

[Nic O'Demus]

Been doing a bit in my late fathers house today. Noticed a single light fitting was flashing dimly every 10 seconds or so, but the light was switched off. When switched on the light works normally, but when switched off it flashes more brightly and more quickly. After a few minutes it settles down to a dim flash every 10 secs or so. Still doing it a couple of hours later. Its a low wattage energy saver type bulb. Could this be the cause, or is it likely to be something more sinister? The house was rewired about 7 years ago, so wiring *should* be good. No mcb's or other devices are tripping. I'll try a conventional bulb in the fitting when I next go over. Any thoughts? Thanks Nic.

[Dave Liquorice]

Is there any other switch controling this lamp, particulary any automatic switch such as a PIR or timer?

Many automatic switches use the circuit through the bulb as the return path for the small amount of power the use. Some CFLs can see this and fire just as you describe. IMHO it's not dangerous per se but the repeated firing of the CFL I suspect will considerably shorten it's life.

[N. Thornton]

Hi, 2 possibilities:

1. its on a PIR detector, CFLs and PIRs have this problem sometimes
2. your switch or wiring is leaking or arcing, in which case it needs attention before anything bad happens.

Regards, NT

[Christian McArdle]

A third possibility is that some other source of radiation is lighting it up. Think radio transmitters, microwave ovens, televisions etc.

To discount it, switch the lighting circuit off at the consumer unit. If it still flashes, the flash energy is not coming down via the electrical system.

Christian.

[Adrian Wint]

This one is easy..... the switch is in the neutral not the live!

Its is wiring error which should be corrected ASAP!

[Al]

I have a fluorescent tube which glows mysteriously when turned off - probably because the switch is in the neutral cable.

[Simon Smith]

This was my first thought also, especially if it is a regular flash every 10 seconds. Does he live next to an airport or military installation? Could also be taxi firm, mobile phoe mast, etc etc although only a radar should give a consistant flash every few seconds.

Simon

[Frisket]

Or 3. Try measuring the voltage on the switched live - we've had quite a few with induced voltages from the loop circuit up to 60v - more than enough to cause a low energy lamp to try and fire when warm. Regards, Richard

[Colin]

Or 4. Try a different light bulb. I have a set of very cheap ones which show this behaviour. (Very annoying in the bedroom!)

I bought a different brand and they don't exhibit the flickering.

Colin

[Joe Green]

Can you please explain how that could cause the problem ?