Why is the light always on after replacing the light fitting?

Question

I replaced the light fitting in our living room, which is controlled by a dimmable switch, and now the light is always on.

When the dimmer is in the off position, the light is not very bright. When I turn the light on by increasing the dimmer setting, the light gradually gets brighter as expected. In the fully on position, when I place my ear next to the dimmer switch, I can hear a buzzing sound. The volume of the buzzing sound gets quieter when I lower the dimmer setting.

While I was changing the light fitting, I turned the light switch to the off position; however, to my surprise still got a small electric shock (it hurt, but I survived).

The light fitting came with two wires: brown and blue. The fitting in the ceiling also has a brown and blue wire, so I connected blue to blue, and brown to brown.

I have a few questions:

1. Did I wire the fitting up correctly? Could it be possible that I just need to wire blue to brown?
2. Is the switch broken?
3. Could there be another issue?
4. Was I wrong (stupid) to assume that turning the light off at the switch was enough to protect me from an electric shock?

Answer 1

Matching colors is usually correct, but there are exceptions. While this is considered the "right" way, it is for safety issues. The light will work either way. But we don't want the power from the brown going down the blue usually neutral in random parts of the wiring.

Which is why turning off the circuit with the switch is usually safe. If the wiring was reversed, with the switch on the blue neutral, the light will still work, but you would have gotten a really nasty full mains shock, instead of the "little" attenuated by dimmer shock. Always kill power to circuits at the breaker before working on them!

Dimmers, when full off, should indeed be full off. The fact it illuminates a light means it is defective. It needs to be replaced. It's not unusual for dimmers to emit a slight 50 hz hum during use, the volume proportional to the current being passed. But they must be able to completely open the circuit.

If you do get another dimmer instead of a regular switch, do ensure the lamps in the fixture are dimmable, and the dimmer is compatible with the lamp type.