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Fujitsu Mini-Split Error Codes

Fujitsu ductless units show errors as blink patterns on the indoor unit lamps, and as numbered codes on a wired remote controller. Below are 7 Fujitsu codes across 3 model series. Each one says what it means, which series it applies to, what you can safely check, and when to call a licensed pro, with a link to the Fujitsu document it comes from.

The same code can mean different things on different series, so match the series column to your unit. Your unit's manual is the final word. Reviewed October 2026.

🔎 Enter the code, blink count or model shown on your unit

7 codes

Fujitsu OPERATION 5 flashes, TIMER 8 flashes, ECONOMY flashingIntake grille not closedAOU9-12-15RLS2 / ASU RLS2 wall-mounted series Fujitsu OPERATION and TIMER flash, ECONOMY flashes fastFault pattern: stop and call serviceAOU9-12-15RLS2 / ASU RLS2 wall-mounted series Fujitsu ECONOMY lamp flashingAir filter cleaning reminderAOU9-12-15RLS2 / ASU RLS2 wall-mounted series Fujitsu Blinks 3 times, at intervals of 21 secondsAir filter cleaning reminder (LPAS series)ASUH18-24LPAS wall-mounted series (with WLAN adapter option)Fujitsu TIMER lamp flashingTimer or clock fault after power interruptionAOU9-12-15RLS2 / ASU RLS2 wall-mounted series Fujitsu OPERATION lamp flashing slowlyAutomatic defrosting in progressAOU9-12-15RLS2 / ASU RLS2 wall-mounted series Fujitsu Two lamps blink while one blinks fastError: use Service check mode on the remoteASUH18-24LPAS wall-mounted series

All Fujitsu error codes

Code	Meaning	Applies to	Safety
OPERATION 5 flashes, TIMER 8 flashes, ECONOMY flashing OPERATION lamp flashes 5 times, then TIMER lamp 8 times, repeating, while ECONOMY keeps flashing	Intake grille not closed	AOU9-12-15RLS2 / ASU RLS2 wall-mounted series	🧭 Check first
OPERATION and TIMER flash, ECONOMY flashes fast OPERATION and TIMER lamps flash while the ECONOMY lamp flashes fast	Fault pattern: stop and call service	AOU9-12-15RLS2 / ASU RLS2 wall-mounted series	🛑 Call a pro
ECONOMY lamp flashing ECONOMY lamp flashes (filter indicator, when enabled at installation)	Air filter cleaning reminder	AOU9-12-15RLS2 / ASU RLS2 wall-mounted series	✅ Keep running
Blinks 3 times, at intervals of 21 seconds Indicator lamp blinks 3 times every 21 seconds	Air filter cleaning reminder (LPAS series)	ASUH18-24LPAS wall-mounted series (with WLAN adapter option)	✅ Keep running
TIMER lamp flashing TIMER lamp on the indoor unit flashes	Timer or clock fault after power interruption	AOU9-12-15RLS2 / ASU RLS2 wall-mounted series	✅ Keep running
OPERATION lamp flashing slowly OPERATION lamp flashes slowly in heating	Automatic defrosting in progress	AOU9-12-15RLS2 / ASU RLS2 wall-mounted series	✅ Keep running
Two lamps blink while one blinks fast Two indoor unit lamps blink while the third blinks fast (ASUH LPAS series)	Error: use Service check mode on the remote	ASUH18-24LPAS wall-mounted series	🛑 Call a pro

✅ Usually fine to keep running · 🧭 Check a few things first · 🛑 Turn it off and call a licensed pro

Find your Fujitsu model series

The codes Fujitsu documents for each series we have checked. If your series is not listed, the code may mean something different on your unit, so check its manual.

More Fujitsu codes

Fujitsu OPERATION lamp flashing slowly: Automatic defrosting in progress

✅ Usually fine to keep running

Applies to: AOU9-12-15RLS2 / ASU RLS2 wall-mounted series. Shows as: OPERATION lamp flashes slowly in heating

The OPERATION lamp lights during normal operation and flashes slowly during automatic defrosting. The manual says defrosting takes a maximum of 15 minutes.

When to call a pro: Not a fault. Call service only if heating does not resume after the defrost cycle.

Source: Fujitsu General Operating Manual (OM) AOU9-12-15RLS2, Indicator Lamp section and Troubleshooting

Fujitsu Two lamps blink while one blinks fast: Error: use Service check mode on the remote

🛑 Turn it off and call a licensed pro

Applies to: ASUH18-24LPAS wall-mounted series. Shows as: Two indoor unit lamps blink while the third blinks fast (ASUH LPAS series)

The manual says that when two lamps blink while the third blinks fast, the owner should check the error code. The code is 2-digit numbers or characters and is read in Service check mode on the remote controller.

When to call a pro: Read the code in Service check mode as the manual describes and give it to authorized service personnel. If the unit beeps multiple times at "00", no error is detected.

Source: Fujitsu General Operation Manual ASUH18-24LPAS, Service check, p.13

Safe first steps for any code

Write down the exact code and how it shows (remote display or number of lamp blinks). Similar codes mean different things on different series.
Turn the system off at the remote, switch off the breaker or disconnect for the unit, wait a few minutes, then turn it back on.
Clean or replace the indoor unit air filters, and make sure nothing blocks the indoor or outdoor unit.
Check that the condensate drain line is not blocked or kinked where you can see it.
Replace the remote controller batteries if the display is dim or the unit does not respond.

🛑 Stop and call a licensed pro if

Any code pointing to refrigerant, the compressor, high pressure or the outdoor unit board. Refrigerant work legally needs a certified technician.
Burning smell, sparks, or a breaker that trips again after a reset.
Water leaking from the indoor unit that does not stop after the drain is clear.

Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician

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