I just moved in into a rented house. Suddenly, usually a few minutes after being turned of, a light bulb goes and flash once.

They're fluorescent and LED lights that flashes once after a random time period (I didn't see any regularity).

It happened at least once on every light.

Any ideas on why it's flashing?

  • Welcome to DIY.SE! Can you provide any more details, like what kind of light bulb (LED, incandescent, etc)> Does it happen after the same amount of time being off? Where in the world are you? – mmathis Sep 27 '16 at 17:38
  • I'm from Brazil. I'll edit the details you asked into the question. – Zero Medeiros Sep 27 '16 at 17:44
  • Are they on a dimmer or something that is not a standard on-off switch? – Mister Tea Sep 27 '16 at 18:36
  • Nope. Just plain old on-offs. – Zero Medeiros Sep 27 '16 at 19:49

A possible explanation: there is something wrong (or intentional) about your wiring such that there is a very weak (high resistance) path for current bypassing the switch.

In some designs of power supplies, the small current will charge an internal capacitor, and when there is sufficient charge it will assume it's been turned on and start supplying power to the LEDs — which then immediately discharges the capacitor, resulting in the brief flash you see.

Perhaps your light switches are illuminated, or they have some sort of special function beyond being a simple mechanical toggle switch. One common reason for this sort of leakage is devices inside the switch which need power and (since there may be no neutral wire at the switch, at least in US wiring) get it by letting a small amount of current through the switched circuit.

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