What does an LED failure look like?
A dark string, a dimmer fixture with an uneven beam, or output that slowly fades and shifts colour — LED sources tend to fail in parts and by degrees.
An LED failure is a fault in the LED source of a fixture: one LED, a string of LEDs or the whole module. The source is many small LEDs, so it often fails in parts or by degrees instead of going cleanly out: a dark string, a dimmer fixture, an uneven beam, flicker, or output and colour that drift over time.
In a series string, one LED that fails open can darken its whole string unless the design has bypass protection. Heat, moisture, surge and age are the usual causes. Total darkness points first at the driver, the supply or a connection, not the LEDs, so those are checked before the module is blamed. A suspected failure is isolated, locked out and proved dead before the fixture is opened.
- Read the symptom. Dark string, dimmer or uneven output, flicker, colour drift, or fully dark.
- Check the pattern. One fixture points at the fixture side; several or the whole circuit points at the loop.
- Isolate. CCR off, locked out and tagged; prove the circuit dead, and earth it if the site procedure requires.
- Look first. Check the lens, seal and housing, the pit for water, and the module face for dark LEDs, discolouration or burn marks.
- Check the supply and driver. Prove them good before blaming the LEDs, then test the module as the manufacturer specifies.
- Repair or replace, then re-test. Replace the module or fixture as the manufacturer specifies, check output and aiming, and record the findings.
A dark string, a dimmer fixture, uneven beam or colour drift points at the LEDs or the module itself.
Fully dark, or flicker across the whole module, points first at the driver, the supply or a connection.
Frequently Asked Questions
Q1What is an LED failure in airfield lighting?
A fault in the LED source of a fixture: a single LED, a string of LEDs or the whole module. It shows as part of the module dark, a dimmer fixture, an uneven beam, flicker, or output and colour that drift over time.
Q2Why does an LED fixture often fail partly or gradually instead of going out completely?
The source is many LEDs, usually wired in strings. One string or one LED can fail while the others keep working, and heat and ageing wear the output down slowly. A filament lamp more often gives a clean on-or-off failure.
Q3Can one failed LED darken a whole string?
In a series string, one LED that fails open can put out the whole string unless the design has bypass protection. How a module behaves depends on its design, so the manufacturer’s data decides.
Q4How is an LED failure told apart from a driver or supply fault?
By the pattern. Part of the module dark, or output falling over time, points at the LEDs. Total darkness, or flicker across the whole module, points first at the driver, the supply or a connection. The supply and driver output are checked before the module is blamed.
Q5What causes LEDs to fail?
Overheating, ageing, moisture reaching the board, surge or electrical overstress, loose or open connections and mechanical damage. Heat and moisture are the common ones, so seals and the thermal path are checked early.
Q6Is it safe to open a fixture with an LED fault?
Only after the circuit is isolated, locked out and proved dead. A series circuit can be at high voltage, up to several kilovolts on a large circuit, and an open-circuited isolation transformer secondary can produce dangerous voltage, so a fixture can be live where it should not be. Follow the site’s permit-to-work and the manufacturer’s instructions.
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