Purpose

The ALC-861(L) family uses different LED configurations depending on model type.
Some fixtures have a single LED, while others use multiple LEDs mounted on a shared circuit board.
Follow the appropriate procedure below based on your fixture type.

Preparation

Open the fixture by unclipping the two clasps and removing the lens and ring to expose the light engine.

Single LED Fixture (White or Blue Taxiway)

Turn off power and lock out the Constant Current Regulator (CCR) before testing.

Set the multimeter to Diode Test mode.

Verify test lead orientation — Red to positive (+), Black to negative (–).

Disconnect the LED light engine from the driver board.

Touch the Red probe to the + (anode) solder point on the LED circuit board.

Touch the Black probe to the – (cathode) solder point.

Observe the LED:

• If it lights up, the LED is functional.
• Some LEDs may appear dim in bright environments — shade the test area if needed.

Expected reading: 1.7 – 3.0 V DC on the multimeter indicates a good LED.

If the LED does not light or reads outside range → Replace the light engine.

Multi-LED Fixture

Fixtures with multiple LEDs use a common circuit board with built-in test points for each LED.

Each LED must be tested individually at its designated test points.

Turn off power and lock out the CCR.

Set the multimeter to Diode Test mode.

Confirm leads — Red to positive (+), Black to negative (–).

Disconnect the LED light engine from the driver board.

Touch the Red probe to the + (anode) test point.

Touch the Black probe to the – (cathode) test point.

Observe the LED:

• If it lights up, that LED is functional.
• Dim light under bright conditions is normal.

Expected reading: 1.7 – 3.0 V DC per LED indicates proper operation.

Repeat Steps 5 – 8 for each LED on the board.

If any LED fails the test → Replace the entire light engine.

 

Safety Reminder

Always maintain safe working conditions by using appropriate personal protective equipment (PPE) where necessary.
Only qualified service personnel should perform diode tests on airfield LED fixtures.
Follow lock out / tag out procedures and verify absence of hazardous voltage before opening fixtures or handling electrical components.

Airport Lighting Company | Troubleshooting Instruction