My LED downlights glow faintly even when switched off — is that dangerous?
Some of our LED downlights glow faintly even when the switch is off — you only notice it at night. They work normally otherwise (this isn't the flickering issue — it's a steady dim glow when they should be *off*).
- Is this a fault, and is it dangerous?
- What causes it — the LEDs, the switch, or the wiring?
- Someone said it can mean the switch is on the neutral instead of the live — is that a real (and serious) thing?
Trying to work out whether to worry or ignore it. What's actually going on?
3 answers
Short answer: a faint afterglow on LEDs when they're "off" is common and usually caused by a tiny residual current still reaching the fitting — because LEDs need almost no power to glow, even a trickle lights them. The usual harmless causes are an illuminated/neon-indicator switch or a dimmer that leaks a little current, or induced voltage in long cable runs. BUT one cause IS a real fault worth checking: if the switch is breaking the NEUTRAL instead of the LIVE, the fitting stays live when "off" — a shock risk when changing a bulb and something to fix. So: often benign, but because one cause is a genuine wiring fault, it's worth having checked rather than assumed.
What's happening (LEDs glow on almost nothing): - Illuminated / neon-indicator switches: a switch with a little locator light passes a trickle of current through the circuit even when off — enough to make an LED glow. Very common cause. - Dimmers / electronic switches: some leak a small current when off; certain LED+dimmer combos glow as a result. - Induced voltage: on long cable runs, a live cable running alongside can induce a small voltage in the switched-off one — enough for an efficient LED. - The fault one — switched neutral: if the wiring switches the neutral rather than the live, the lamp holder stays live when the switch is off. The LED may glow, but the real problem is it's a shock hazard (live fitting when you think it's dead) and it's incorrect/unsafe wiring.
Is it dangerous? - The benign causes (indicator switch, dimmer leakage, induced voltage) aren't dangerous — just annoying, and there are fixes (a bleeder/CR "snubber", a non-illuminated switch, or LED-friendly dimmers). - The switched-neutral fault IS a safety issue and should be corrected — you never want a fitting live when it's switched off.
How to tell / fix: - Because one cause is a wiring fault, the safe move is to have a licensed electrician test whether the switch is breaking live or neutral and check for leakage. If it's just an indicator switch or dimmer, they'll sort the glow cheaply; if it's a switched neutral, they'll correct the wiring.
Common mistake: assuming it's "just cheap LEDs" and ignoring it — usually true, but not always, and the exception is a live-when-off fitting. Get it checked once, then you know. Anyone had the glow turn out to be a switched neutral?
Ours turned out to be the illuminated switches — the little locator light was trickling just enough through to make the LEDs glow at night. Swapped to non-illuminated switches on those and the glow stopped. But I'm glad we had it checked rather than assumed, because the switched-neutral possibility is the one you don't want to shrug off — a fitting that's live when it's "off" is exactly the kind of thing you'd only discover the hard way changing a bulb. Cheap to test, worth knowing which cause it is.
Useful to know LEDs glow on basically nothing — with old halogens you'd never have seen it because they need real power to light. So the glow is partly just LEDs being ultra-efficient and showing up leaks that were always there. The fix for the harmless version can be as simple as a different switch or a little snubber device. Only the switched-neutral case is a proper fault. Get someone to confirm which before spending on new bulbs you don't need — it's rarely the bulbs.
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