Fujitsu Aircon Blinking Light Guide
Fujitsu units encode faults through a two-LED blink counting system — operation light for the first digit, timer light for the second. Reading the code correctly depends on counting both LEDs while the economy light flashes to confirm an active error.
What each indicator light on a Fujitsu indoor unit does
Fujitsu indoor units use three LEDs whose roles differ from most other brands — the economy lamp doubles as the fault alert, while the operation and timer lamps encode the two-digit error number.
| LED | Color | Role |
|---|---|---|
| Operation lamp | Green or red (varies by model) | Running status — encodes first digit of fault code when blinking |
| Timer lamp | Orange or green (varies by model) | Timer status — encodes second digit of fault code when blinking |
| Economy lamp | Green | Energy-saving mode — flashes continuously when a fault is active |
Wall-mounted units: three-LED layout
Most Fujitsu wall-mounted units in Singapore (ASAG and ASTG series) have three LEDs on the front panel. The operation lamp shows running status. The timer lamp indicates timer function or encodes part of the fault code. The economy lamp shows energy-saving mode status and also serves as the fault alert indicator.
LED colors vary by model generation — older units use red for operation and green for timer, while newer ASAG and ASTG models use green for operation and orange for timer. The color assignment changes between series, so counting the blink pattern matters more than the color itself.
Ceiling cassette models: no front-panel LEDs
Ceiling cassette models (AUXG series) have LEDs on the indoor PCB behind the panel grille, not visible from the room. The same fault logic applies but reading the blinks requires opening the unit or using a wired remote with display diagnostic mode. If your cassette shows no light at the grille but the unit has stopped, check whether the wired remote displays a fault code before assuming the unit is fully dead.
Normal Fujitsu indicator light behavior — not a fault
Before counting blinks, rule out the patterns that are part of normal operation. These are commonly mistaken for faults.
A steady operation light means the unit is running normally. A slow intermittent blink on the operation light means standby or delayed start. The operation light staying on with no airflow for the first few minutes after startup is normal compressor protection delay. A steady timer light means the timer function is active. A steady economy light means energy-saving mode is running.
A brief rapid blink on the operation light alone (without the economy light flashing) can indicate a defrost cycle or internal startup checks. This resolves on its own within a few minutes.
| Pattern | What it means |
|---|---|
| Steady operation light | Unit running normally in cooling or dry mode |
| Slow intermittent blink (operation light) | Standby mode or delayed start with timer active |
| Operation light on, no airflow for a few minutes | Compressor protection delay after power cycle — normal |
| Steady timer light | Timer function is active |
| Steady economy light | Energy-saving mode active (reduced output) |
How Fujitsu encodes error codes through LED blinks
Fujitsu's two-LED counting system assigns each LED to one digit of the fault code, with the economy lamp confirming an error is active.
Reading the blink count
When a fault occurs, the economy light starts flashing continuously — this confirms an error is active. At the same time, the operation LED blinks a counted number of times for the first digit and the timer LED blinks a counted number of times for the second digit. A pause separates each sequence, then the pattern repeats.
For example, if the operation LED flashes 2 times and the timer LED flashes 6 times, the error code is 26 (drain problem). If the operation LED does not flash at all and the timer LED flashes 3 times, the code is 03 (communication failure during operation). Count carefully and watch for at least two full repetitions to confirm.
Wired remote and stored fault codes
On units with a wired remote controller, error codes appear on the LCD display as alphanumeric codes. When the display shows EE:EE, press the Energy Save and Zone Control buttons simultaneously for 3 or more seconds to reveal the stored error code.
Only one error code displays at a time. If multiple faults exist, subsequent codes appear only after the first fault is resolved. Stored codes persist in memory even after power is turned off.
Once you have the code
Fujitsu uses a numeric code system: the 02 to 08 range covers communication faults, the 22 to 34 range covers temperature sensor failures, and the 50 to 75 range covers motor, compressor, and protection faults. The outdoor PCB also has its own LED blink count independent of the indoor unit. The full Fujitsu error code lookup table is on the dedicated Fujitsu error code page.
How multi-split Fujitsu systems display faults differently
Multi-split Fujitsu systems distribute fault signals across connected indoor units depending on whether the fault is at the shared outdoor unit or isolated to a single indoor unit.
When all indoor units blink at the same time
On a Fujitsu multi-split system (AOTG or AOYG outdoor unit with multiple ASAG indoor units), all units share the same communication line and refrigerant circuit. A fault on the shared outdoor unit causes every connected indoor unit to show blinking lights.
If only one indoor unit blinks while the others run normally, the fault is isolated to that unit — typically a thermistor, fan motor, or wiring connection issue specific to that indoor unit. Each indoor unit may store a different error code even when the root cause is a shared outdoor fault, so check each unit individually.
Communication wiring requirements
Communication errors (codes 02 to 05) are the most common multi-split fault pattern. Longer wiring runs and more connection points increase the chance of signal issues. Fujitsu specifies stranded wire only between indoor and outdoor units — solid wire can cause intermittent communication faults that are difficult to trace.
Larger outdoor units with four LEDs
Some larger Fujitsu multi-split outdoor units (like the AOY30) have four LEDs labelled A, B, C, and D to indicate which refrigerant circuit has the fault. Single-split outdoor units have just one red LED. On a four-LED outdoor unit, identify which LED is flashing before reading the blink count — each letter corresponds to a specific indoor unit circuit.
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