Your new LED lamp flickers, keeps glowing when it's off, buzzes or doesn't work at all. Sound familiar? Almost always the problem isn't the lamp itself but the combination with the dimmer, the transformer or the wiring. In this guide you'll find the 10 most common LED problems with cause and solution, plus the installation mistakes you're better off avoiding from the start.
In short
- LED lamp flickers? Usually an unsuitable dimmer or an old halogen transformer.
- Lamp glows after it's switched off? Often an illuminated switch or residual current in the wiring.
- Lamp fails quickly? Usually too much heat in an enclosed fitting.
- Doesn't light at all? Check plus/minus on 12V, the starter on fluorescent tubes and the power supply.
Already know what you're looking for? Jump straight to the right products:
Quick diagnosis: what's going on?
| Symptom | Most likely cause | Solution |
|---|---|---|
| Flickers or blinks | Dimmer not suitable for LED | LED dimmer with a low minimum |
| Flickers on 12V spotlights | Old halogen transformer | Replace with an LED power supply |
| Glows faintly when off | Illuminated switch or residual current | Ordinary switch or a base load |
| Hums or buzzes | Dimmer or transformer | Different dimmer or LED power supply |
| Doesn't light at all (12V) | Plus and minus reversed | Turn the lamp or wires around |
| LED tube doesn't light | Old starter or ballast | LED starter or the right tube |
| Fails quickly | Too hot in an enclosed fitting | Lamp for enclosed fittings |
| LED strip only half lit | Voltage drop or power supply too small | Feed from both ends, larger power supply |
| Doesn't dim properly (jumps, buzzes) | Lamp not dimmable or dimmer too heavy | Dimmable lamp, matching dimmer |
| Lamps have a different shade of white | Different Kelvin or brands | Same Kelvin and same series |
1. LED lamp flickers or blinks
The most searched-for LED problem. The cause is almost always in what sits in front of the lamp:
🎚️ Old dimmer
Dimmers made for incandescent bulbs often have a minimum of 40 to 60 watts. A 5-watt LED lamp never reaches that, so the dimmer starts to flicker. Choose an LED dimmer with a low minimum, from 2 or 3 watts.
🔁 Halogen transformer
Electronic halogen transformers also need a minimum load. With a few 2-watt LED spots you won't reach it. Replace the transformer with an LED power supply.
🔌 Loose connection
A poor contact in the socket, a terminal block or the switch can also cause blinking. Screw the lamp in firmly and have loose wires checked.
⚡ Heavy appliances
Does the lamp flicker briefly when the washing machine or air conditioner kicks in? Then the voltage dips for a moment. A quality lamp with a good driver is less affected.
You can read more on this subject in dimmable LED lighting: everything about dimmers.
2. LED lamp glows on or burns faintly when it's off
A faint glow or the occasional flash while the switch is off. This happens because an LED lamp needs so little power that a tiny bit of residual current is enough to make it glow.
- Illuminated switch or switch with an indicator light: it always lets a small current through. Replace it with an ordinary switch.
- Switch on the neutral instead of the live wire: the lamp then stays live. Have an electrician check this.
- Long wires side by side (for example with a two-way switch setup): they can transfer a little current. An electrician can fit a base load or a suppression capacitor.
- Smart switch without a neutral wire: it always needs a little current. Choose a smart switch with a neutral wire, or fit a base load.
3. LED lamp or dimmer buzzes
A soft hum or buzz usually comes from the dimmer or the transformer, rarely from the lamp. Dimmers work with leading-edge or trailing-edge phase control; LED lamps are often quieter on a trailing-edge dimmer. A universal LED dimmer picks the right method by itself.
Matching products:
Cord dimmer with plugDim a floor or pendant lamp with no DIYView ›
LED strip dimmer PWM 12/24VFlicker-free dimming of LED stripsView ›
Dimmable LED lamp E27, 800 lumensWarm white 2700K, dims wellView ›
Dimmable GU10 spot (35 mm)3W replaces 30W, 4000KView ›
4. LED lamp doesn't light at all
➕➖ 12V lamps
G4, MR16 and car bulbs often run on direct current. If plus and minus are the wrong way round, the lamp does nothing. Turn it around. See the difference between AC and DC.
🏭 Fluorescent tube
New LED tube not lighting? Then the old starter is still in, or the tube doesn't match the ballast. Follow the step-by-step guide to replacing fluorescent tubes.
🔌 Wrong power supply
A 24V LED strip doesn't light (or barely does) on a 12V power supply. The other way round, the strip gets damaged. Always check the voltage.
💡 Socket or contact
An old, bent contact tab in the E27 socket sometimes doesn't touch the shorter LED base. Switch the power off and carefully bend the tab up a little.
G4 bi-pin lamps 12V DC, 5 piecesNote: run on direct currentView ›
LED power supply 12V DC, 24WStable direct current, no flickerView ›
📩 Handy overview, isn't it?
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5. LED lamp fails too quickly
A good LED lamp lasts 15,000 to 25,000 hours. If it fails within a year, there's almost always a clear cause:
- Too hot: the electronics of an LED lamp don't like heat. In a small, enclosed fitting or a recessed ceiling spot with no room behind it, it gets too hot. Choose a lamp that's suitable for enclosed fittings.
- Moisture: a lamp without the right IP rating in the bathroom or outdoors. See IP rating explained.
- Wrong dimmer: a non-dimmable lamp on a dimmer, or a dimmer that doesn't suit LED, stresses the driver and shortens its lifespan.
- Voltage spikes: during thunderstorms or from heavy appliances on the same circuit. Quality lamps have better protection against this.
6. LED strip only half lit, getting dimmer or showing odd colours
📉 Voltage drop
With long strips (often from 5 metres on 12V) the end is dimmer or yellower than the start. Solution: feed the strip from both ends, or choose 24V.
🔋 Power supply too small
Add up the wattage of all the metres and take a power supply with a 20% margin. An overloaded power supply switches off or makes the strip blink.
🌈 RGB colours are wrong
Red and green swapped? Then the wires are in a different order on the controller. Swap the connections or set the order in the app.
✂️ Part doesn't light
You may only shorten a strip at the cut mark. A poor solder or clip connection is the most common cause of a dark section.
More about strips in indirect lighting with LED strips. A worked example for choosing the right power supply is in AC and DC.
7. Dimming doesn't work properly
The lamp jumps on and off, only dims a little or flickers at low settings. Check these three things:
- Is the lamp dimmable? It says so on the packaging. A non-dimmable lamp should never go on a dimmer.
- Does the dimmer suit LED? Choose an LED dimmer with a low minimum and a maximum that matches the total wattage.
- Set the minimum. Many LED dimmers have an adjustment screw for the lowest setting. Turn it up a little if the lamp flickers at the bottom.
Dimmable R7s linear lamp 118 mm1000 lumens, for uplightersView ›
Universal LED dimmer 3–250WLow minimum, picks leading or trailing edge by itselfView ›
8. Lamps have a slightly different shade of white
Two 3000K lamps can still look a bit different, especially from different brands or series. For one room, always choose the same type from the same series. Also look at colour rendering (CRI, Ra): the higher, the more natural the colours. More in colour temperature explained.
9. Lamp is less bright than expected
Compared on watts instead of lumens? A 5-watt LED lamp isn't automatically as bright as a "50-watt" halogen spot. Look at the number of lumens and the beam angle: a narrow beam gives a bright spot, a wide beam a softer light over a larger area. See what is a lumen?.
10. Lamp changes colour or turns yellower
After years the phosphor layer of an LED can age, making the light slightly yellower. With a lamp that runs far too hot, this happens faster. Make sure there's enough ventilation and choose quality lamps.
Installation mistakes you're better off avoiding from the start
| Mistake | Result | How to do it right |
|---|---|---|
| Keeping the old dimmer | Flickering, buzzing | LED dimmer with a low minimum |
| Keeping the old halogen transformer | Flickering, not lighting | LED power supply of the right voltage |
| Choosing by watts | Too dark or too bright | Choose by lumens |
| Wrong IP rating | Moisture, fails quickly | IP44 bathroom, IP65 outdoors |
| Lamp in an enclosed fitting without ventilation | Fails quickly | Lamp for enclosed fittings |
| Illuminated switch | Afterglow | Ordinary switch |
| Mix of brands and Kelvin | Uneven light | One series and one Kelvin per room |
| LED strip with no margin on the power supply | Dropouts, blinking | 20% margin on the power rating |
| Plus and minus not checked | Lamp doesn't light | Check polarity on 12V DC |
| No lighting plan | Shadows or dark corners | Plan first, then buy |
You can read the step-by-step installation in installing LED lamps in five steps and the guide to installing LED lighting.
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Frequently asked questions
Why does my LED lamp flicker?
Why does my LED lamp glow faintly when it's off?
Is a flickering LED lamp dangerous?
Can I put a non-dimmable LED lamp on a dimmer?
Why do my LED spots in the ceiling fail so quickly?
My LED strip is dimmer at the end, how come?
Is switching LED on and off often bad for it?
Kind regards,
Bas / LEDPLANET.NL