LED tape that glows when off has a small current reaching it through a path that should be open: a leaky dimmer, a lit switch, or a switch on the DC side. Tape that flickers or drops out near the bottom of the dimmer is a different fault, a load or a low-end setting. Test for each one separately.
The bar is closed, the dimmer is off, and the bottle shelf is still a faint line of light. The usual reaction is a bigger dimmer or a new reel. Neither touches the cause, and the first one can make it worse. Our LED strip troubleshooting guide covers the other faults on an installed run.
Glow When Off: Three Leak Paths
A strip that is “off” glows when something still feeds the driver or the strip. LED tape needs very little power to show a visible glow, so a few milliamps are enough. Three paths cover most cases.
1. The dimmer leaks at off. Many wall dimmers do not open the circuit completely when they are off. Niko explains that a two-wire dimmer has no neutral and takes its own operating current through the connected load. With an incandescent lamp that current did nothing visible. With an LED driver on the circuit, it can be enough to charge the driver’s input and push a faint output to the tape. According to Lutron’s support notes on ghosting, this shows up with loads that are too small for the dimmer or not on its tested list.
2. The switch has a light in it. An illuminated or locator switch passes a small current through the load to light its own indicator. Leviton names this as a common cause of ghosting and makes LED-compatible illuminated switches to avoid it.
3. Long cable runs couple voltage. Niko also points to capacitive coupling between long cables in the same raceway: a switched leg running beside a live conductor for a long distance can pick up enough voltage to make LEDs glow. This is the case where the dimmer is fine and the glow still appears.
- 1Dimmer leakageTwo-wire dimmerDraws its supply through the load
- 2Lit switchLocator lightSmall current through the driver
- 3Coupled cableLong shared racewayVoltage picked up on the leg
- 4DC-side switchDriver stays poweredLeak across the switch
Where the Switch Sits on a 24V System
On low-voltage tape, where the circuit is broken matters as much as which device breaks it.
- Line side. The switch or dimmer interrupts the driver’s input. With the driver unpowered there is nothing to feed the tape, apart from the leak paths above.
- DC side. A switch, a sensor or a cheap dimmer interrupts the 24V output while the driver stays powered. Forum users on All About Circuits and other electronics forums report faint glow and flicker in this arrangement, attributed to leakage across the switch and to the switching supply’s own filter. It is a reading of forum experience, not a test, but it matches what installers see.
If the design needs control on the DC side, use a component built for it, such as a 0-10V decoder like our UT-C010-350 that sits between the driver and the strip and is driven by a 0-10V control, rather than a plain switch in the DC wires. For plain on and off, switch the line side of the driver.
A related symptom: a large driver lightly loaded can fade out slowly after switch-off instead of stopping at once, because its internal capacitors drain through the small load. A long fade on a short run is a sizing note, not a fault.
Low-End Flicker and Dropout
Flicker that appears only near the bottom of the dimming range, or tape that cuts out before the dimmer reaches its lowest setting, comes from the dimmer and the driver disagreeing about where “low” is.
A published example shows how large that disagreement can be. In a WAC Lighting dimming report for one of its tape drivers, the same Lutron dimmer model flickers below 32% in ELV mode and dims to 6% in TRIAC mode. Same dimmer, same driver, different setting, a five-fold difference in the usable low end.
Three fixes, in order:
- Set the dimmer mode to match the driver. A dimmer with selectable phase has to be set to the method the driver is listed for. Our UT-D60-24-TRC is built for forward and reverse phase dimmers; a 0-10V driver needs a 0-10V control and ignores phase-cut entirely.
- Raise the low-end trim. According to Lutron’s support notes, when lights flicker only at the bottom of the range, the fix is to raise the dimmer’s low-end trim until the light is stable. The bottom of the range then sits where the driver can follow it.
- Change the pairing. If the trimmed low end is still too high for the space, use a combination that has been tested to a lower level, or move to 0-10V control, which separates the dimming signal from the power. Our dimming guide compares the methods.
Load Below the Dimmer Minimum
Phase dimmers are built with a minimum load. A short run of tape on a driver can sit below it, and the dimmer then behaves erratically: it may not turn the load fully off, it may flicker at every level, or it may not turn on at all at low settings.
Installers on the Mike Holt forum describe exactly this with ELV dimmers and LED tape: not enough load “to register,” and short tape runs that flicker at shut-off. The dimmer’s spec sheet gives its minimum; the tape driver’s spec sheet gives the input power at your actual run length. Compare those two numbers, not the dimmer’s maximum rating and the tape’s total watts on the drawing.
A bigger dimmer does not help here. A dimmer with a higher capacity often has a higher minimum load as well, which is why it can make the glow worse. The fixes are to group more load on the dimmer, to choose a dimmer listed for small LED loads, or to dim on the 0-10V side so the phase dimmer is not in the circuit at all.
A 10-Minute Test Sequence
Run these with the circuit as installed. Each test changes one thing.
| Test | Result | Points to |
|---|---|---|
| Turn the breaker off | Glow stops | Leak through the dimmer, switch or coupled cable |
| Breaker off, glow continues for minutes then fades | Slow fade | Driver capacitors draining into a small load |
| Replace the dimmer with a plain switch for the test | Glow stops | Dimmer leakage |
| Plain switch still glows | Glow continues | Illuminated switch, or coupling on the switched leg |
| Disconnect the switched leg at the driver input and meter it with the switch off | Voltage present | Coupling or a miswired leg |
| Run the dimmer from 100% down slowly | Flicker starts at one level | Low-end trim or mode mismatch |
| Add a second load on the same dimmer for the test | Flicker or glow stops | Load below the dimmer minimum |
Write down the level where flicker starts and the dimmer and driver models. That record goes into the pre-install test sheet for the next job, so the same pairing is not installed twice. Our guide to Class 2 drivers covers the driver side of the circuit, and the driver placement guide shows where to keep the driver reachable for these tests.
Is a Faint Glow a Safety Problem?
Usually not in itself. The current behind a ghost glow is small, and on a properly wired circuit it is the dimmer or the switch doing what it was designed to do with a load it was not designed for. It is still a defect on a commercial job: owners read it as “the lights are broken,” and guest rooms, patient rooms and theaters need real darkness.
Two cases deserve a closer look. A glow that stays steady, without fading, after the breaker is off means voltage is reaching the circuit from somewhere else, such as a shared neutral, a miswired leg or another circuit, and that needs an electrician’s investigation before anything else. A glow together with a warm dimmer, a buzzing driver or a burnt smell is no longer ghosting; isolate the circuit and treat it as a fault.
Fixes That Work and Fixes That Do Not
Fixes that work, matched to the cause:
- Dimmer leakage: a dimmer with a neutral connection, a dimmer listed for low-wattage LED loads, or a load adapter where the dimmer maker offers one.
- Illuminated switch: a switch without a locator light, or an LED-compatible illuminated switch.
- Coupling: separate the switched leg from live conductors, or switch the driver with a relay close to it.
- DC-side switching: move the switch to the line side, or use a decoder built for DC-side control.
- Low end: set the mode, raise the trim, or change to 0-10V.
Fixes that do not work: a bigger dimmer, a new reel of tape, or a different color temperature. All three change the load or the product without touching the path the current is taking.
The dimming method of each of our drivers is listed on the drivers, controllers and connectors page.
