When LED lighting misbehaves, systematic troubleshooting beats guesswork. Here’s my approach to diagnosing common LED problems in commercial installations.

The Basic Troubleshooting Framework

Before diving into specifics, remember the fundamentals:

1. Gather information: What exactly is the problem? When did it start? What changed?
2. Isolate the scope: One fitting, one circuit, one area, or everywhere?
3. Check the obvious: Power supply, connections, settings
4. Narrow down: Use substitution and elimination to identify the culprit
5. Verify the fix: Confirm the problem is resolved, not just masked

Most LED problems fall into predictable categories. Let’s work through them.

Problem: Fitting Won’t Turn On

Step 1: Check power supply

• Is there voltage at the fitting? Use a multimeter.
• Check the circuit breaker or fuse.
• Check any switching upstream (time clocks, sensors, contactors).

Step 2: Check connections

• Are terminals secure?
• Any signs of loose or corroded connections?
• For retrofit tubes, are the lamp pins properly seated?

Step 3: Check the driver

• Many drivers have indicator LEDs. Is it showing fault?
• Can you hear any noise from the driver (clicking, buzzing)?
• If accessible, check driver input voltage.

Step 4: Substitute to isolate

• Swap the suspect fitting with a known-good one.
• If the new fitting works, the original fitting is faulty.
• If the new fitting also doesn’t work, the problem is upstream.

Common causes:

• Faulty driver (most common LED failure point)
• Connection failure
• Incorrect wiring (especially after installation or modifications)
• Power supply issues

Problem: Fitting Flickers

Covered in detail in my earlier article, but the summary:

Constant rhythmic flicker (50/100Hz):

• Driver issue (poor smoothing)
• Dimmer incompatibility
• Check minimum load on dimmer circuits

Random intermittent flicker:

• Loose connection (most common)
• Voltage fluctuation
• Load switching elsewhere on the circuit

Flicker on multiple fittings:

• Supply voltage issues
• Dimmer or control equipment
• Power quality problems

Diagnosis approach:

• Check connections
• Try bypassing the dimmer
• Measure supply voltage stability
• Substitute fittings to isolate

Problem: Fitting Dims or Fails Intermittently

Thermal shutdown:

• LEDs and drivers reduce output or shut down when overheating.
• Check ambient temperature vs rating.
• Check for obstructed ventilation.
• Is the fitting recessed without thermal insulation clearance?

Failing driver:

• Intermittent function often precedes complete failure.
• Check driver status indicators.
• Listen for abnormal sounds.

Poor connection:

• Connections that work when cool can fail when warm (thermal expansion).
• Retighten connections.

Problem: Wrong Light Output

Too dim:

• Check if dimming controls are activated (scene settings, sensors).
• Verify wiring is correct (some drivers default to low output if dim signal is floating).
• Check for voltage drop on long runs.
• Fitting may be approaching end of life (LED degradation).

Too bright:

• Less common, but check dimming settings.
• Verify correct product was installed (wattage/lumen spec).

Uneven brightness across fitting:

• LED module partially failed.
• Driver not powering all LED sections.
• Manufacturing defect.

Problem: Wrong Colour

Colour temperature wrong:

• Verify correct product (4000K vs 5700K looks very different).
• Check if tunable white feature is incorrectly set.

Colour inconsistent between fittings:

• Products from different batches can have slight variation.
• One fitting from different source/time.
• Mixed manufacturers.

Colour shifted from original:

• LED degradation (phosphor aging).
• Indicates fitting approaching end of useful life.
• May be accelerated by overheating.

Problem: Sensor-Controlled Lights Misbehave

Lights don’t turn on when occupied:

• Sensor blocked or aimed incorrectly.
• Sensor failed.
• Time delay set too long.
• Control circuit issue.

Lights don’t turn off when vacant:

• Sensor detecting movement from other sources (HVAC vents, moving objects).
• Sensitivity too high.
• Detection zone reaching into adjacent spaces.
• Hold time set too long.

Lights turn off while occupied:

• Occupant not in detection zone.
• Sensitivity too low.
• PIR sensors need movement; stationary person not detected.
• Hold time too short.

Diagnosis approach:

• Walk the space observing sensor indicator lights.
• Adjust sensor position/aim if needed.
• Adjust sensitivity and time delay settings.
• Consider different sensor technology for challenging spaces.

Problem: DALI System Issues

DALI troubleshooting is its own topic, but basics:

No communication:

• Check DALI bus voltage (should be around 16V).
• Check polarity (DALI is polarity-sensitive on some equipment).
• Look for short circuits on the bus.
• Verify controller is online and configured.

Individual fitting not responding:

• Check fitting DALI address assignment.
• Verify physical connection to bus.
• Try re-addressing the fitting.
• Swap with known-good fitting to isolate.

Group/zone not working:

• Check group assignment in controller.
• Verify all fittings in group are addressed correctly.
• Look for communication errors in controller logs.

When to Call for Help

Some problems exceed field troubleshooting:

Power quality issues: Fluctuating voltage, harmonic distortion, and similar issues need power quality analysis equipment.

Complex control system problems: Networked lighting management systems might need manufacturer support.

Systematic failures: If multiple fittings from the same batch are failing, it could be a product recall situation.

Safety concerns: Any sign of burning, melting, or arc damage requires immediate isolation and investigation.

Documentation

For every troubleshooting call:

• Record the symptom
• Document what you checked
• Note what you found
• Record what you did to fix it
• Verify the outcome

Good records help with warranty claims, pattern identification, and training others.

The Troubleshooting Mindset

Most LED problems have logical explanations. The trick is systematic investigation rather than jumping to conclusions.

Start broad (is there power?), narrow down (which component?), verify with substitution (is it really the driver?), and confirm the fix.

Experienced troubleshooters develop intuition about likely causes, but intuition backed by systematic method beats pure guesswork every time.

And when you can’t figure it out—ask. Manufacturer technical support, industry forums, and colleagues have seen problems you haven’t.

There’s no shame in learning from others’ experience.