just noticed that a light switch (mechanical, not a dimmer; 220v 50hz) is buzzing at audible volume (can hear in 20cm), when both keys are on (first: traditional lightbulb, second: 23w energy saving bulb - with all that electronics inside).

Didn't opened the switch so dunno how it is wired (common phase.. or a common ground - if an installation point is powered by two wires, a drunk specialist may have used them the wrong way), it is known that this connection is split from wall sockets/main room lightning (yes, two switches outside the house!).


  • pressing key 2: energy-saving bulb enabled, no sound
  • 2, then 1 (normal bulb): sound.
  • 2, ..some time, 1: sound
  • 1, 2: sound
  • sometimes, no sound at any combination.

Guessing that a bulb is possibly broken and sends a high-freq noise that forms an arc.. Unfortunatelly can't get a single normal bulb today to test if it forms a noise, too.

1 Answer 1


There are a couple of possibilities: the most likely is that the switch is worn and should be replaced. If the switch makes a good connection sometimes and a bad connection at other times, you would hear the noise only occasionally.

If your local laws allow you to do the work yourself, I think this would be an easy task. The steps would be (at least in the US where I am):

  1. turn off the circuit breaker;
  2. remove the switch cover plate;
  3. double-check that there's no voltage at the switch in both on and off positions;
  4. unscrew the wires from the switch
  5. screw the wires onto the new switch
  6. reinstall the new switch and cover plate.

Another possibility, but much less likely, is that there's a loose connection between the switch and one of the wires. The steps to fix this would be the same as for replacing the switch, but tighten the screws on the wires instead of removing the wires.

  • 1
    The inside of the switch may also be wet, if so find the source of the water then replace the switch.
    – Walker
    Jan 19, 2011 at 12:33

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