In most of the flicker calls we take, the strip itself is fine. The fault sits somewhere between the wall switch and the first metre of tape: the dimmer, the driver, a joint or the cable run.
That’s good news, because it usually means a cheap fix. The trick is reading which kind of flicker you’ve got. Each pattern points to a different cause, and working through them in order saves a lot of guesswork.
One safety note first. Anything on the mains side of the driver, including wall dimmers and switches, is work for a registered electrician. The low voltage checks below are fine to look at yourself with the power off.
Start With The Phone Camera Test
Point your phone camera at the strip and watch the screen. If you see rolling bands or strobing that your eyes can’t pick up, the strip is being dimmed with low frequency PWM. The LEDs are switching on and off faster than you notice, but not fast enough for a camera.
For a hallway at home, that may never matter. In an office, a gym, or a retail space where staff film content for social media, it matters a lot. Some people also feel low frequency flicker as eye strain or headaches after a few hours.
The fix is a driver or controller with a higher PWM frequency. When you’re choosing controllers from our LED sensors and control gear range for screen-heavy or filmed spaces, ask us about PWM frequency before you buy.
It Flickers When Dimmed But Is Fine At Full Brightness
This is the most common one we see. The dimmer and the driver aren’t compatible.
A standard wall dimmer controls the mains supply, so it needs a driver designed to be dimmed that way. Put a non-dimmable driver behind it and you’ll get flicker, buzzing or an early failure. The other culprit is minimum load. Plenty of older wall dimmers were designed for 300 watts of halogen. A 40 watt LED run sits below their minimum, so they can’t regulate properly at the low end.
Matching the dimmer to the driver solves it. Our LED power supplies and control systems include triac dimmable and DALI options, and for commercial jobs we usually recommend DALI or 0 to 10V control over wall dimmers.
The Whole Run Blinks Every Second Or Two
That rhythmic on, off, on, off is the driver protecting itself. It’s overloaded or sees a short circuit, cuts out, tries again, and repeats.
We recommend loading a driver to about 80 percent of its rating. Five metres of 14.4 watt per metre strip draws 72 watts, which calls for a 100 watt driver rather than a 75 watt one. We walk through the maths in our guide to calculating LED strip length and power supply size.
If the driver is sized correctly and it still blinks, look for a short. Stray copper at a cut, a pinched cable or a damaged connector will trigger the same behaviour.
It Starts Flickering After Twenty Minutes
Time-delayed flicker is almost always heat. The driver warms up, hits its thermal limit, cuts back, cools and restarts.
We find these drivers stuffed into sealed ceiling cavities, jammed behind joinery, or sitting in a shop window cabinet that cops the afternoon sun. Move the driver somewhere with airflow and give it more headroom on its load.
Only The Far End Flickers Or Looks Dim
That’s voltage drop. The further power travels along the strip, the more voltage it loses, and by the end of a long 12V run there may not be enough left for the LEDs to hold steady.
Feed the run from both ends or from the middle, use heavier cable between the driver and the strip, or move to 24V for longer runs. Cheaper strip with thin copper tracks makes the problem worse, which is one reason we only stock quality LED strip lighting built for commercial use.
One Section Flickers And The Rest Is Fine
Look at the joints. Clip-on connectors hold their pins against the copper pads with light pressure, and heat cycles, vibration or a slamming door can break that contact. For permanent installs, a soldered joint is far more reliable.
Moisture is the other suspect. A waterproof strip that’s been cut and never resealed will corrode from the cut end. Green or black discolouration on the pads is the giveaway, and the section usually flickers for a few weeks before it dies. Strip bent too tightly around a corner can also crack its circuit board, causing a fault that comes and goes.
It Glows Or Flickers Faintly When Switched Off
This is ghosting. A small current is leaking through to the driver even when the light is off. Illuminated or smart switches, a switch wired on the neutral, and long cable runs can all cause it. This one is for your electrician.
It Flickers When Something Else Starts Up
If the flicker lines up with a heat pump, a chiller compressor or commercial kitchen gear kicking in, the mains voltage is dipping as the motor starts. Quality drivers ride through those dips. Budget ones don’t. We see this most in food display cabinets, where the strip and the compressor share a circuit.
A Five Minute Check Before You Call Anyone
- Run the phone camera test.
- Turn the dimmer to full. If the flicker stops, suspect compatibility.
- Feel the driver after half an hour. Too hot to hold means a heat problem.
- Check every joint and connector along the run.
- Note when it happens and what else is running at the time.
That list usually narrows it to one cause. If you’d rather get it right before anything goes in the ceiling, our lighting design team checks driver sizing and control compatibility at the planning stage. Give us a call with the symptoms and we’ll help you track it down.
