Quick answer
A buzzing light switch is a loose terminal, a failing dimmer module, or a dimmer that is not LED-compatible driving LED lamps. The dimmer causes are a nuisance; a loose terminal is a fire risk, because it means current is arcing across a poor connection inside a plastic accessory in a wall. You cannot tell which it is from the sound alone.
Common causes
- Loose terminal arcing inside the switch
- Failing dimmer module at end of life
- Incompatible phase-cut dimmer driving LED lamps
- Dimmer overloaded beyond its rated wattage
- Worn switch mechanism with degraded contacts
- Loose connection in the ceiling rose or junction feeding the circuit
What you can do now
- 1Switch the lighting circuit off at the DB board if the switch is hot or discoloured
- 2Note whether it buzzes only when dimmed, which points at the dimmer rather than a terminal
- 3Feel the switch plate — warmth means stop using it now
- 4Check whether LED lamps were fitted to an old dimmer, a very common cause
- 5Do not remove the faceplate yourself
When to call a professional
Book within the week, and immediately if the switch is warm, discoloured or smells hot. A loose terminal is a fire risk in a wall cavity, and there is no way to distinguish it from a failing dimmer without opening the accessory. An electrician will check the terminations, replace the switch or fit a correctly rated LED dimmer.
Typical cost in Johannesburg
Switch/dimmer R450–R750
Indicative ranges only. We provide written, itemised quotes before any work.
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