WiremanWireman · LED glows or flickers when off: troubleshooting for electricians · 2023 NEC ·
LED glows or flickers when off
Faint glow or blinking with the switch off. Usually a lit switch, a smart control or induced voltage.
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How it works
An LED needs only a few milliamps to glow, far less than an incandescent bulb needed. With the switch off, a tiny current can still reach the lamp: through the pilot light in a lighted switch, through the electronics of a smart switch or sensor that has no neutral, or by capacitive coupling from a nearby hot wire running alongside the switched leg. Old filament bulbs soaked that current up without showing it; LEDs show it as a glow or a blink. The one dangerous cause is a switch that opens the neutral instead of the hot.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What does the light do after you turn it off?
- Fades out within a few secondsNormal driver afterglow
- Stays faintly lit or blinks the whole timeWhat’s on the wall?
- A switch with a light in the toggleThe switch’s pilot light leaks current through the lamp
- A smart switch, dimmer, timer or sensorIs a neutral (white) wire connected to the control?
- No neutral connectedA no-neutral control powering itself through the lamp
- Yes, neutral is connectedTest: Measure at the fixture with the switch offExpect: Near 0 V on LoZ. A regular meter may show some volts on an open wire; that alone isn’t a problem.
- About 120 V, even on LoZThe switch is opening the neutral, not the hot
- Some volts on regular V, near 0 on LoZInduced (coupled) voltage on the switched leg
- Near 0 V on bothThe lamp itself
- A plain switchTest: Measure at the fixture with the switch offExpect: Near 0 V on LoZ. A regular meter may show some volts on an open wire; that alone isn’t a problem.
- About 120 V, even on LoZThe switch is opening the neutral, not the hot
- Some volts on regular V, near 0 on LoZInduced (coupled) voltage on the switched leg
- Near 0 V on bothThe lamp itself