Because something is letting a tiny current reach the lamp even when “off”. Common culprits are: - Illuminated or smart switches and some dimmers that leak a small standby current. - Capacitive coupling in long or parallel cable runs (especially 2‑way switching), creating a “ghost” voltage. - Poor‑quality LED drivers that react to microamps of leakage. - Shared/borrowed neutrals or wiring errors that back‑feed the lamp. That minuscule current slowly charges the LED driver until it discharges as a brief flash, or it keeps the LEDs glowing. Typical cures: replace illuminated/smart/two‑wire dimmers with LED‑compatible or 3‑wire types, fit an anti‑flicker RC snubber across the lamp, use better lamps/drivers, correct neutrals/polarities, or shorten/change cable routes where practical.
🏠Homeowner view
LEDs flicker or glow when off because a very small current is still getting to the lamp. That trickle can come from: - Illuminated switches, two‑wire dimmers, or smart switches that need a standby supply. - “Ghost” voltage induced in the cables, especially on long switch drops and 2‑way circuits where conductors run side‑by‑side. - Sensitive or low‑quality LED drivers that react to very small leakage. - Neutrals shared with other circuits, or a wiring mix‑up that back‑feeds the light. Practical things you can try: 1) Swap the lamp for a known good, quality LED (many include a bleed resistor to stop glowing). 2) If the wall switch has a glowing indicator, replace it with a non‑illuminated type. 3) If you have a smart switch with only two wires (no neutral), change to a 3‑wire smart switch that has a neutral, or add the maker’s approved bypass. 4) If it’s on a dimmer, fit an LED‑compatible trailing‑edge dimmer with a low minimum load. 5) Ask an electrician to add an anti‑flicker module (RC snubber) across the lamp or at the switch. 6) On 2‑way circuits or long cable runs, a snubber or different wiring layout often helps. 7) If more than one light is affected, have the neutrals and terminations checked—shared or loose neutrals can cause back‑feed. Most fixes are quick: the right switch/dimmer, a small snubber, or a better lamp usually stops the flicker.