What's normal for a dimmer
Dimmers control brightness by chopping the power many times a second, and some of that energy becomes heat in their electronics. A plate that is slightly warm with the lights on, and a soft hum you only hear up close, are within what many dimmers do. Smart switches with their own electronics can feel faintly warm too.
A dimmer should not be too hot to keep a finger on, and the noise should not change sharply as you move the knob, get louder over the months or come with flickering. A dimmer carrying more lights than it is rated for runs hot, and one made for old halogen globes often buzzes with LEDs.
Buzzing, crackling and heat at an ordinary switch
A standard switch has no electronics, so any sound means current is jumping a gap, at a loose terminal behind the plate or worn contacts inside the mechanism. That small arc makes heat, blackens the contacts and can char the switch body. A switch that feels spongy, needs a firm press or makes the lights flicker as you touch it is often at the same stage.
Energy Safe Victoria lists old or broken switches, and sparks from switches, among the warning signs of faulty wiring. Its advice is that changing a light switch is not a DIY job.
LEDs and dimmers that don't match
Plenty of homes changed to LED globes or downlights without changing the dimmer. LED drivers and older dimmers often disagree, and the result can be buzzing at the switch or the light, flicker at low settings, or lights that glow faintly when off. The fix is a dimmer matched to the drivers, or drivers matched to the dimmer. When we replace a dimmer, we check the load and compatibility of every light on it and test the connections behind the plate.
What you can safely do now
- Turn off a switch that is crackling, hot or smells of hot plastic, and leave it off.
- If the switch is too hot to touch, switch the lighting circuit off at the switchboard if it is safe to reach.
- Don't remove the switch plate or tighten anything behind it.
- Note whether the noise changes with the dimmer setting, and which lights that switch controls.
- If there is smoke, fire or immediate danger, get everyone out of the house.
Services that can help
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Related questions
- Why do my LED lights buzz or hum?Most buzzing LEDs come from a mismatch rather than a fault: a dimmer built for old halogen globes, an LED driver that doesn't suit the dimmer, an old transformer left in…
- Why is my power point warm?A plug that feels slightly warm after a heater or kettle has run for a while can be normal.
- Why can I hear crackling in my walls or ceiling?Most creaks and ticks in walls and ceilings come from timber, roofing and pipes expanding and contracting, or from animals.
- Are old round or Bakelite light switches safe?Many still work, but age is the concern, not the shape.
Sources for this answer
2 sources, with the date each was checked
- 1.Energy Safe Victoria: Old switchboards, particularly those without a safety switch Old power switches or power points, particularly broken ones Flickering lights Sparks from switchboards, switches or power points. If your house is over 30… Accessed 30 September 2026.
- 2.Energy Safe Victoria: Electrical work isn’t a DIY job, even for small jobs such as changing power points or light switches. Accessed 30 September 2026.
General information for homes in Victoria. Every installation is different, so treat this as a starting point. Where this answer refers to Victorian safety or rental rules, the sources above have the current requirements.