Dimmers control the light by dropping some of the power inside the switch, and that makes a little heat. A faceplate that feels a bit warm is normal. One that's too hot to keep your hand on, has gone yellow or brown, or smells is a different story.
If yours is in the second group, switch it off and ring 0421 772 661. We'll find out whether it's overloaded, mismatched to the lights or failing.
If the dimmer plate is discoloured, melting, crackling or there's a burning smell, turn the lights off at the dimmer, then turn off the lighting circuit at the switchboard if it's safe to reach. Leave it off until it's been checked. If there's smoke or flame, get everyone out and call 000.
Don't take the faceplate off, and don't swap the dimmer yourself. Dimmers are wired to mains voltage and replacing one is licensed electrical work. Touch the plate only lightly with the back of your fingers to judge warmth.
A good dimmer running a sensible load should feel no more than mildly warm, a bit like a phone charger. These signs mean it's working harder than it should, or something inside or behind it is breaking down:
If you pull your hand away, it's running beyond what it's comfortable with. Turn it off.
Discolouration around the knob or the edges is a sign of sustained heat over months or years.
A faint hum can come from LED and dimmer mismatches. Crackling or sizzling suggests a poor connection or arcing.
Any burning or fishy smell near a switch is a reason to switch the circuit off and call us.
Count the lights on that dimmer. Every dimmer has a maximum load. A dimmer controlling a long row of old halogen downlights can easily be at or over its limit. Multiple dimmers sharing one plate usually have to be de-rated, so they handle less each.
Check the globes are dimmable. Look at the box or the globe itself. Non-dimmable LEDs on a dimmer can cause heat, flicker and buzzing. Our guide to dimmer switches buzzing with LEDs explains the mismatch in more detail.
Compare full brightness with low settings. Note whether it's hotter dimmed down or at full. That detail helps us work out whether it's the dimmer type, the load or a connection.
Notice what changed recently. New globes, extra lights added to the circuit or a new dimmer are often where the trouble started.
Too much load. Halogen downlights draw much more power than LEDs, so an older dimmer controlling several of them is working hard all the time. Moving to LED downlights with a matching dimmer usually solves both the heat and the power use.
The wrong type of dimmer for LED. Dimmers work in different ways (often described as leading edge and trailing edge). LED drivers usually prefer one type, and an older dimmer designed for halogen and iron-core transformers can run hot, hum or flicker with LEDs. The fix is a dimmer listed as compatible with the LED fittings.
A loose terminal behind the plate. A screw terminal that has worked loose makes heat right at the connection, which can show up as a hot plate even with a modest load. This is the one we worry about most, because it can get worse quickly.
The dimmer is simply failing. Electronic parts wear out, especially in a dimmer that has run hot for years. If the load is reasonable and the globes are right, replacing the dimmer is often the answer.
Call an electrician if the dimmer is hot rather than warm, discoloured, noisy or smells, or if lights on it flicker or fail. We check the connections, measure the load, confirm the dimmer and LED drivers suit each other and replace what's needed. If the plate is getting warm but nothing else is wrong, we can usually tell you quickly whether it's within normal limits.
If a power point near the dimmer is also warm, read power point hot to touch, and for a burning smell anywhere, follow what to do about a burning smell straight away.
Yes, slightly. Dimmers turn some power into heat when they dim. It should feel mildly warm, not hot enough that you want to pull your hand away.
Usually because the dimmer wasn't designed for LED loads, or the globes aren't dimmable. A compatible dimmer and dimmable LEDs normally run cooler.
A dimmer that overheats or has a loose connection is a fire risk, which is why we say to switch it off and have it checked if it's hot, discoloured or smells.
That may reduce heat a little but doesn't fix an overload or a loose connection. Treat it as a stop-gap until it's checked.
No. Dimmers connect to mains wiring and replacing one is licensed electrical work in NSW.
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