LEDs light up though switch - why is that?

If you turn off LEDs and they continue to shine without power the confusion is often great. What can be the cause of this behavior of the lamps, and what you can do to fix this, read this post.

Cause of afterglow

Reason for the afterglow of the LED lights are not the LEDs themselves. Reason for the afterglow are always the conditions on site.

Fundamental to the appearance of the afterglow is that LEDs as a light source need very little power to activate. Unlike a light bulb, LEDs can cope with minimal amounts of electricity.

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

Applied voltages

The reason why there is tension at all can be different.

  • outdated follower relay (voltage is on the control wire here)
  • electromagnetic induction through adjacent cables
  • Glimmlampenschalter (these are almost never compatible with LED lights)
  • not suitable dimmers

Induction occurs when a live cable is very close to the LED light or the incoming cable. The minimum field radiated from the cable with current flow induces a voltage in the lamp or in the feeding cable. These minimum induced voltages already suffice for the lamp to glow or flash.

You can easily replace the follower relay, you should replace conventional glow switches (illuminated switches) with conventional ones and of course always use a suitable dimmer.

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

Tips & Tricks

Dimmable LEDs usually glow weakly, not dimmable flashes usually only briefly. Both points to the same phenomenon and cause: applied voltage. To remedy this, you must eliminate the cause of the voltage.

Video Board: Why some LED bulbs glow or flash when turned off