LEDs light up although the switch is off - why is that?

If you switch off LEDs and they continue to light up even without power, the confusion is often great. Read this article to find out what can be the cause of this behavior of the lamps and what can be done to remedy it.

Cause of afterglow

The reason for the afterglow of the LED lights is not the LEDs themselves. The reason for the afterglow is always the local conditions.

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Fundamental to the occurrence of afterglow is that LEDs as light sources require very little electricity to activate. Unlike a light bulb, LEDs use minimal amounts of electricity.

You can therefore assume that there is a (minimal) voltage on the lamp itself. A conventional light bulb would not have responded to this voltage because it would have been too weak. LEDs then make this "current error" visible.

Applied tensions

The reason why a voltage can be present at all can be different.

  • obsolete follow-up relay (voltage is on the control wire here)
  • electromagnetic induction through adjacent cables
  • Glow lamp switches (these are almost never compatible with LED lights)
  • not matching dimmers

Induction occurs when a live cable is very close to the LED light or the incoming cable. The minimal field that is radiated by the cable with current flowing through it induces a voltage in the lamp or in the supply cable. These minimal induced voltages are already sufficient for the lamp to glow or flash.

You can simply swap overrun relays, you should replace glow switches (illuminated switches) with conventional ones and of course always use a suitable dimmer.

You can also turn off the afterglow by connecting the largest possible resistor in front of the lamp, which does not allow any current to flow in the OFF position.

Tips & Tricks Dimmable LEDs Glimmer usually weakly, non-dimmable flashes usually only briefly. Both point to the same phenomenon and the same cause: applied voltage. To fix it, you need to fix the cause of the voltage.